Film and television adaptation of literature has become the mainstream of current film and television works, but literature and film and television, as two different art forms, the adaptation process is very complicated. This paper deeply discusses the various forms of adaptation of original works and the reasons behind them through case studies and qualitative analysis. At the same time, the article points out that there are significant differences between the original literature and the adaptation of film and television, and analyzes the reasons and techniques of adaptation. Meanwhile, taking the film and television adaptations of the Four Great Classical Novels and Sherlock as examples, it specifically analyzes the content and plot changes presented after the adaptation, and points out that the purpose of film and television adaptation is to improve the viewing quality and satisfy the needs of modern audiences.