Objective To explore the correlation between the genetic dissimilarity and heterozygosity of mates and the patho?genicity of Schistosoma japonicum in the definitive host. Methods By using seven microsatellite loci markers,S. japonicum genotyping of sixteen pairs randomly mated was performed,the genetic dissimilarity and heterozygosity were calculated between the mates,and the correlation between the genetic dissimilarity and heterozygosity of the mates and the pathogenicity of S. japon?icum in the definitive host was evaluated. Results There was a significant correlation between the genetic similarity of S. ja?ponicum mates and the mean number of eggs per worm pair in the liver and intestinal tissue (r = 0.501 6 ,P < 0.05;r =0.796 5,P<0.01,respectively)and the hatching rate of deposited eggs in the liver(r=0.508 3,P<0.05),respectively. There was no correlation between the genetic similarity of the mates and hepatosplenomegaly per worm pair(r=0.109 5,P>0.05;r=0.265 3,P>0.05,respectively)and the average diameter of granuloma in the liver(r=-0.272 7,P>0.05),respec?tively. There was no correlation between the heterozygosity of the mates and all the pathological parameters of S. japonicum in the definitive host(P > 0.05). Conclusions There is the correlation between the genetic dissimilarity of the mates and the pathogenicity of S. japonicum in the definitive host,and the genetic dissimilarity is greater,pathogenicity is weaker. There is no correlation between heterozygosity of the mates and the pathogenicity of S. japonicum in the definitive host.