Abstract: RNA interference is a double-stranded RNA molecules inducing gene silencing process,which can be reflected at the transcriptional level or post-transcriptional level.Design of RNAi for multiple target gene sequences,RNAi library for building biology and systematic screening is a powerful tool for medical research.The current study of the tumor,RNAi library has incomparable advantages.It has been widely used for tumor-related genetic screening,drug screening and target tumor cells to overcome drug resistance and other fields.In this paper,RNAi and RNAi library technology and applications in cancer research were done a review.