Objective:To investigate the infection status of Yersinia in the main host animals of plague in Xiahe and Luqu counties, the Himalayan marmot plague foci of Gansu Province, and to provide a basis for exploring the epidemic status of plague in these foci. Methods:Samples of the ileocecal region and contents, pharyngeal swabs (or tongue roots), and blood of the main host animals of plague in Xiahe County and Luqu County where the plague were active in the 1950s and 1960s were collected from 2014 to 2018. The Yersinia isolation, virulence determination and F1 antibody detection were performed, respectively. Results:Totally 24 strains of Yersinia were detected in 958 samples of ileocecal region and contents with a bacterial detection rate of 2.51%, which were 13 strains of Yersinia enterocolitia (Y.e), 1 strain of Yersinia kristensenii (Y.k), 2 strains of Yersinia frederiksenii/ intermedia (Y.f/i), 6 strains of Yersinia intermedia (Y.i), 1 strain of Yersinia aldouae (Y.a) and 1 strain of Yersinia massiliensis (Y.m). Totally 19 strains of Yersinia were detected in 958 samples of pharyngeal swabs (or tongue roots), and the detection rate was 1.98%, which were 8 strains of Y.e, 1 strain of Yersinia pseudotuberculosis (Y.p), 4 strains of Y.k, 1 strain of Y.f/i, 4 strains of Y.i, and 1 strain of Yersinia ruckeri (Y.r). The virulence types of 21 strains of Y.e were ail -ystA -ystB +yadA -virF -rfbc -, ail -ystA -ystB -yadA -virF -rfbc -, respectively, accounting for 9.52% (2/21) and 90.48% (19/21), none were pathogenic. The results of F1 antibody in 1 079 serum samples were all negative. Conclusions:Yersinia are widely found in the pharynx and intestines of the main host animals of plague in Xiahe and Luqu counties, and the Y.e detected are all non-pathogenic strains. The results of this investigation can provide clues for further study on the preservation of Yersinia pestis in host animals and their living environment.