The introduction of double-stranded RNA (dsRNA) into cells can effectively and specifically lead to the degradation of corresponding mRNAs in a gene-dependent manner, which is defined as RNA interfering (RNAi). This powerful technology has been widely employed to manipulate gene expression in mammalian and human cells, elucidate signal pathways and identify gene functions in a whole-genome scale. Simultaneously, many pharmaceutical companies are very interested in the research and development of RNAi-based drugs for various diseases, especially in cancers. In present review, we attempt to recapitulate the potential application of this breakthrough technology in many aspects of cancer gene therapy such as genome-scale screens, target identification and validation, functional analysis and animal models for diverse diseases.