[Abstract] Objective to evaluate the prevalence of mice Polyoma Virus in laboratory mice in Beijing by PCR and Serology tests. Method: IFA method was used to test 197 mice sera which were selected from the submitted samples to out monitoring center during 2011-2012. In the 197 samples, 130 sera were from those breeding facilities; and 67 sera were from those experimental facilities. A POLY virus specific primer pair was used in PCR to detect POLY virus from intestines contents of 80 mice which were from breeding facilities. Result: 130 sera from breeding facilities were negative for Polyoma Virus; there were 7/67 POLY virus positive samples from those experimental facilities. A 272bp Polyoma Virus specific amplification can be detected in experimental infected mice. There were no specific amplification in the 80 samples from breeding facilities. Conclusion: the POLY virus pollution were not detectable by the current serological and PCR methods in breeding facilities in the past 2 years: the prevalence of mice Polyoma Virus in experimental facilities can not be neglected. An annual surveillance including POLY virus is necessary not only in productive facilities, but also those experimental facilities.