To understand the changes in the number and the genetic mechanism of Himalayan Marmot(Marmota himalayana),4 geographical populations(Delhi,Ulan,Tuotuohe and Ando) living in the Qinghai-Tibet Plateau were investigated using microsatellite data.Eight microsatellite loci were selected as the molecular markers.The allele numbers,effective allele numbers and polymorphism information content were estimated to characterize genetic diversity.Tests to detect excess heterozygosity in a population at mutation-drift equilibrium were analyzed.The results show that all loci were high polymorphism,the allele numbers,effective allele numbers and polymorphism information content were 4.75,3.033 2 and 0.610 2,respectively.The expected heterozygosity and the observed heterozygosity were 0.670 and 0.699.Tests of departures from Hardy-Weinberg equilibrium indicated many loci with significant heterozygosity excess at P<0.05.As a conclusion,the Himalayan marmot population living in the Qinghai-Tibet Plateau has a relatively rich diversity;The Ando populations were significantly different from mutation-drift equilibrium with heterozygote excesses,they had suffered bottleneck effects in the past as well as the recent population decline.