Objective To observe the dynamics of F1 antibody and immunoglobulin M (IgM) in cats after vaccinated Yersinia pestis,to discuss the significance of detection of F1 antibody and IgM in surveillance of animal plague.Methods The 3 cats were vaccinated Yersinia pestis on their backs with muhipoint hypodermic injection and blood samples were collected via femoral vein on 3rd to 521st days after injection.F1 antibody was detected by sandwich Enzyme-linked immunosorbent assay (ELISA),and IgM of F1 antibody was determined with a capture antibody.Results After vaccinated Yersinia pestis for 3rd days,F1 antibody and IgM appeared slightly positive,with the titer of 1 ∶ 22.00 and 1 ∶ 20.33,respectively.The titer of F1 antibody increased to 1 ∶ 25.33 on the 4th day,and reached the peak of 1 ∶ 29.67 on the 97th day,kept 1 ∶ 25.33 on the 521st day.While the titer of IgM reached peak of 1 ∶ 212.00 on the 7th to 10th days,and decreased rapidly to below the positive standard on the 30th day.Conclusions Detection of F1 antibody in cats with plague by sandwich ELISA can trace plague prevalence in animals back to a long time,which may be applied for investigation of plague foci.A single serum sample can determine early animal plague with a capture antibody to detect IgM of F1 antibody in cat with the plague,and a single serum sample tested with the two methods at the same time for detection of F1 antibody and IgM can precisely verify the infection time of plague in animals for 3 to 7 days.