Objective To investigate the natural infection rate of Mouse Adenovirus(Mad)in Guangdong province and to estimate the tissue distribution and serology changes of Mad in infected mice. Methods Serums of mice from general environment of Guangzhou in 2007 and 2015, and the SPF mice from12 supervision and 32 entrusted units of Guangdong province among 2013~2015 were detected by ELISA.Thirty-six 3 weeks old BALB/c mice were each intraperitoneally inoculated with 0.2 mL of Mad in 4.5×10⁶ copies/μL concentration. The tissue samples, including heart, liver, spleen, lung, kidney, brain, stomach, cecum contents and serum were taken at 0 d before inoculation, and 3, 7, 10, 15, 18, 21, 30, 37, 44, 51, 60 d after inoculation (3 animals each time).Real-time fluorescent quantitative PCR (Q-PCR) method was used to detect the virus nucleic acid of tissue. In addition, the antibody against Mad was detected by ELISA.Results Antibody positive rate was 24.44%~84.15% and 0% among the general environment mice and the SPF mice, respectively, which is given priority to with Mad-2 K87 serotype strains. There were no clinical manifestations among all infected mice.The virus nucleic acid positive rate was 100% (3/3) in all tissue samples in 3 d and 7 d, which maintained a longest time to 60 d in spleen. Besides the liver, virus nucleic acid content were highest at 7 d in each tissue of infected mice, with spleen highest (5.5×10⁵ copies/μL), heart was second at 3.4×10⁵ copies/μL, cecum contents and stomach ranked third (2.6×10⁵ copies/μL), followed by brain (0.8×10⁵ copies/μL). The antibody could be successfully detected at 15 d after inoculated, hit the peak at 37 d and maintained a high level until 60 d.Conclusions Mad infection rate is low in SPF mice, high in general environment mice.Mad nucleic acid content is the highest and positive rate maintain the longest in spleen,suggesting that Mad mainly replicate in spleen. And 7 d is the best pot for nucleic acid testing.Serum neutralizing antibody can be used as a monitoring index within 15~60 d after infection.