Objective To study the infectivity of Pasteurella pneumotropica (P.pneumotropica) from different sources between laboratory rats and mice. Methods 30 laboratory rats and mice were inoculated with 3 %P.pneumotropica% isolates from rats, mice and wild mice, to compare the biologic characteristics, by SDS_PAGE, Western blot and RAPD_PCR, of the 3 isolates at different days of post_inoculation with that before inoculation. Results Laboratory rats and mice were infected easily by 3 %P.pneumotropica% isolates, which were carried in them until the end of the test (4w). lsolates reobtained from post_inoculated animals had no difference distinctly in biologic characteristic, protein component, antigenic bands and genotype. Conclusion The same isolate of %P.pneumotropica% can infect both laboratory rats and mice.