Racial discrimination is a historical issue that can be traced back to the 19th century. In the period of time, blacks couldn’t get equal treatment, they were humiliated, scolded even abused and tortured by whites. After the declaration of Emancipation Proclamation, black people began to win some respect from other races little by little. In the United State, racial discrimination in southern America is more serious the North America. In fact, in the period of writing, Harper Lee not only coincides with the crisis of the great depression, but also coincides with the black civil rights movement. We can find traces from the novel, such as food shortage and economic decline. The southern American is covered by a group of dark clouds, which betoken racial discrimination. In the course of the 1930s two million people became homeless, with middle-class quickly overthrown. The United States experienced the most serious economic crisis in the world history. At the same time, as the weakest group in American society, American blacks were miserable. They were still suffering under the yoke of slavery.
Harper Lee was born in a small town in southern United States in 1926. Her father was a lawyer and a former state legislator. When she graduated from local public school, Harper Lee decided to enter the University of Alabama to study law. And one year later, she went to the University of Oxford in the United Kingdom for further study as an exchange student. After six months of graduation, she left school and moved to New York to pursue her dream of writing. As a representative of the southern writers in America, Harper Lee created an excellent work which reflected the real situation and problems in the South of the United States.
Many critics think that Harper Lee has a remarkable genius for telling stories. The characters she writes in the novel are almost lifelike in appearance and all blend into one harmonious whole. She tries to describe the stories in the small town from a six years old child's perspective. This method mixed both child's and adult's observation. It will help people understand the simple motivation and unquestioned tradition in a complex condition. With the changing of Scott’s perspective, Harper Lee describes a dark and decadent society. She tries to expose the severe racial persecution and racial discrimination in the presence of American society and reflect the harsh reality blacks suffer in the United States. She tries to explore the significance of survival to rouse black cultural consciousness, including the awakening of female consciousness. 
2    Literature Review
It is no exaggeration to say that the novel To Kill a Mockingbird has been the most popular realistic novel about racial discrimination in America. Since the publication of the novel, it had been widely praised by readers and critics. Lots of scholars at home and abroad have already done researches about this novel. And the methods and the point of views they used are different. Xu (2014) advocates the theme about this novel is morality. According to her, the story, based on the period of the Great Depression in the United States, reveals the darkness and corruption of human nature and attacks the racial prejudice in society through the growth of Scott in mantel. The author explores the depth of human nature by convincing the readers that there is still good and justice in human beings. Wang (2015) analyzes the Gothic literary expression Harper Lee used in the novel. Harper Lee gives the novel a more artistic charm by adopting Gothic style in the whole novel. In the form of autobiography, it tells in detail the experience of a lawyer and his three children in a town in southern United States in the period of Depression. She thinks To Kill a Mockingbird is one of the most representative works of Harper Lee and maintains the main reason is the author reveals social situation and existing problems in the novel. Su (2012) tries to use a different point of view to look at this novel by analyzing it from a child's perspective and tone. From the personal experience and narration of Scott, the writer criticizes the hypocritical phenomenon of ruined moral degeneration. In her paper, Scott is the main character in this book. Along with the progress of the story, Scott’s opinion changed gradually. Liu (2002) holds that geographical element is one of the most important factors which influence the writing style of the writer. Although the American Southern literature falls into the category of the American literature, it has formed another style which distinguishes itself from other styles in America literature gradually. And one of the reasons which lead to this change is the war. Because of the Civil War, works in that period had deep south regional color. The novel was a typical southern story which happened in a town in 1930s. The racial relations, loneliness, equality and justice, which were revealed in the novels, were the common problems in southern America. Li (2012) thinks that from the perspective of language, it cannot describe completely everything of human life. Therefore, symbolism has become a common artistic expression in literary works. Under the guise of symbolism, writers like using images to express their intention. And mockingbird is familiar to American people. So in lots of American works, mockingbird usually is favored by writers. They give different meanings to this image. 《杀死一只知更鸟》中知更鸟的象征意义(2):http://www.youerw.com/yingyu/lunwen_48354.html