Forecast of the heterosis of Small Tail Han sheep crossed with imported meat sheep by genetic polymorphism of microsatellite DNA was done in different sheep breeds. The gene frequency, the polymorphism information contents, the number of effective alleles, the heterozygosity, and the genetic distances were studied in four imported meat sheep and Small Tail Han sheep using five microsatellite loci. The crossing effects on the Small Tail Han sheep with four imported meat sheep were tested. The results indicate that there are genetic polymorphisms at five microsatellite loci in five sheep breeds. Five microsatellite loci can be used for genetic diversity evaluation in sheep breeds. The genetic variability of Dorset is the highest, and that of the Small Tail Han sheep is the lowest in the five sheep breeds. The order of heterosis from large to small in four imported meat sheep by the analysis of genetic relationship is White-Suffolk, Black-Suffolk,Dorset, and Texel. This accords with the testing results of actual heterosis. It is feasible to forecast the heterosis of Small Tail Han sheep crossed with imported meat sheep by genetic polymorphism of microsatellite DNA, which will have an important value for sheep breeding in the future.