Abstract: RNA interference(RNAi)is a mechanism existing in eukaryotes, which can specifically degrade target gene mRNA directed by homology double strand RNA (dsRNA) and result in post transcriptional gene silencing (PTGS).At first, the long dsRNA is cut by endonuclease Dicer, into 21~23 nt small interference RNA which named siRNA.And then siRNA inhibits the translation process of target gene mRNA by recognizing and degrading target gene mRNA. In this paper, the mechanism, production and application of RNAi in fishes were reviewed.