Abstract: In this paper, partial sequence of horse DRD4 gene was cloned including intron1, partial exon1 and exon2. And restriction enzyme Stu I was used to analyze the polymorphism of the DRD4 gene sequences of 270 horses from 6 types including importing breed, cultivating breed and local breed. The products of digestion with restriction enzyme StuⅠ were detected by 8% nondenatured polyacrylamide gel electrophoresis and showed in silver staining protocol.The result indicated restriction enzyme Stu I showed polymorphism. Six kinds of genotypes were found in six populations , which were controlled by three alleles. The results of χ2 test showed that genotypes frequency of horse DRD4 gene in TB, SH, XN did not fit with Hardy-Weinberg equilibrium(P < 0.05), but that in WS, BH and WZ fit with Hardy-Weinberg equilibrium(P＞0.05) .