Peony is an endemic species with high ornamental value in China, 49 varieties were collected to examine their esterase isozymes by polyacrylamide gel plate electrophoresis. A total of 34 isozyme bands presented, they could be divided into 3 regions. The Rf of first region is 0.14~0.26; of the second region 0.31~0.66, and the Rf of third region ranges 0.70~0.92. Based on the frequency of each isozyme band, the dissimilarity values were calculated, and 8 groups could be distinquished by Q type cluster analysis. Furthermore, the dissimilarity coefficients between and within these groups were calculated and the map of genetic distance coefficients is finally illustrated.