Piwi-interacting RNA (piRNA) was discovered in 2006 and is a class of small non-coding RNAs (sncRNAs) which interaction with the PIWI family. piRNAs is the largest class of small non-coding RNA molecules expressed in animal cells. In order to supply a comprehensive source about piRNA related SNPs, we developed a public database piRSNP. We comprehensively identified SNPs on mouse piRNAs by mapping.