Abstract: In order to study the genetic diversity of genuine medicinal materials Xi Pinellia ternata(Thunb.)Breit. In Xinyang Xi County, ISSR is used to amplify the 24 P. ternata. 8 ISSR primers with clear amplification bands are selected, 117 obvious bands are detected, of which 110 bands are polymorphic, and the mean polymorphism information content(PIC) is 0.850 8. The average observed number of alleles (N_a), effective number of alleles(N_e), Nei's genetic diversity index (H) and Shannon's information index(I) are 1.927 9, 1.481 1, 0.292 7 and 0.448 1, respectively. Cluster analysis by UPGMA shows that 24 P. ternata are divided into three groups at a genetic similarity of 0.590 1. The results show that there are high genetic diversity among 24 P. ternata.