Tan sheep,a special Mongolia sheep breed in China,is famous with its delicious meat and slow growth rate. In our study,a total of 29 high polymorphic microsatellite markers were used to screen 96 Tan sheep individuals,which were sampled from the basic ewe population in Yanchi Tan sheep reservation farm in the Ningxia Hui Autonomous Region,China. Analysis of genetic diversity,population structure and co-relationship between molecular genotype and measured phenotype(body weight and body size traits)of the 96 samples were carried out,and the following results were obtained:the average(Na)and mean effective(Ne)numbers of alleles,the average expected heterozygosity(He),the average observed heterozygosity(Ho),and the average polymorphism information content(PIC)were 9.5,4.5,0.72,0.64 and 0.69,respectively. The sampled population held high genetic diversity,the correlation between MAF33 and body height and chest depth existed,and BMS1788 was associated with rump height and chest circumference. Also,5 microsatellite markers including BL41,BMS835,BOVILS56,MAF33 and BMS500 were significantly correlated with the cannon circumference. These six microsatellite loci may be useful in further marker-assisted breeding for Tan sheep.