Objective:To analyze the epidemic situation of plague among animals in the foci of Meriones unguiculatus in Inner Mongolia Plateau, and to find out key influencing factors affecting the epidemic of the plague, and to provide theoretical basis for the prediction, early warning and risk assessment of the plague. Methods:The monitoring data including gerbils density, gerbils body flea index, plague epidemic intensity, etc., as well as environmental data including temperature, precipitation and El Ni?o activity (Southern Oscillation Index, SOI) from 19 banners (counties, cities and districts) in Ulanqab Plateau area, the foci of Meriones unguiculatus in Inner Mongolia Plateau were selected. The methods of correlation analysis, structural equation model and rank correlation were used to analyze the epidemic and key influencing factors of plague among animals in the foci. Results:The plague epidemic cycle in the foci of Meriones unguiculatus in Inner Mongolia Plateau was 5 to 10 years. The correlation analysis results showed that all the factors had influence on each other. Structural equation model screened out that the main influencing factors of plague epidemic were SOI, gerbils density and temperature. SOI had a negative effect on plague epidemic intensity (-0.022) and temperature (-0.029), while gerbils density had a positive effect on plague epidemic intensity (0.014), and temperature had a negative effect on plague epidemic intensity (-0.065). In rank correlation, when the gerbils density was at a high value, the probability of high plague epidemic intensity in that year was 4/9; when SOI was at a low value, the probability was 5/9; when the temperature was at a low value, the probability was 5/9. When the plague epidemic intensity was at a high value in that year, the probability of the plague epidemic intensity being high in the following year was 5/8; when the gerbils density was at a high value in that year, the probability was 4/9; when SOI was at a low value in that year, the probability was 4/9. Conclusion:Climate and biological factors can affect prevalence of plague, and countermeasures should be taken in advance to prevent plague outbreaks when El Ni?o phenomenon, low temperature, high density of gerbils, and high previous-year prevalence of plague appear.