There were found Mousepox Virus (MPV) acute or chronic infection in laboratory mice.Seven,three,two and one acute infection of MPV occurred in Kunming,NIH,ICR and BALB/c mice respectively in near 10 years.MPV chronic persistent infection was demonstrated by immunofluorescence assay(IFA). Both retrospective and prospective epidemiological surveys confirmed that IFA positive was related to outbreak of Ectromelia. IFA should be applied for monitoring chronic persistent infection of MPV in mice.