Abstract: Objective To understand the duration of F1 antibodies in the sera from plague patients in convalescent period and the effectiveness of three detecting assays of indirect hemagglutination test(IHA), double-antigen sandwich enzyme-linked immunosorbent assay(DAgs-ELISA)and colloidal gold immunochromatography(GICA). Methods Twenty five serum samples from plague patients in convalescent period were detected with IHA, DAgs-ELISA and GICA, respectively. Results Among the 25 serum samples, 19, 21 and 18 were detected to be positive in IHA test, DAgs-ELISA and GICA, respectively. F1 antibody titers were 1∶80-1∶320 in 15 positive samples in IHA test, and 1∶640-1∶1280 in 10 positive samples in DAgs-ELISA. Conclusion F1 antibodies could be detected in convalescent sera in most plague patients by conducting three assays above mentioned, indicating they are sensitive and specific in plague detection.