Key frame extraction is the precondition and fundamental of the video retrieval and video analysis. The method of key frame extraction determines the final result of video analysis. Firstly, the paper introduced the basic theories and principles of the Key frame extraction technology. Secondly, examined the typical method of key frame extraction techniques of video based on non-compression domain and compression-domain in detailed, at the same time, the evaluation and comparisons of the methods are made by experimental. Thirdly, the summarization is given and the prospection of Key frame extraction in the future is made in the end of paper.