Abstract: Genetic heterogeneity of glucosephosphate dehydrogenase (6—PGD) from firststrimester chorionic villi and frequencies of the Hans of Xi'an was analysed by starch-gel electrophoresis. The Studies demonstrates that genetic heterogeneity of 6—PGD has existed in first trimester chorionic villi, the bands of it can be of equal intensity to the erythrocyte samples. In our population samples (n=144) the following frequencies were calculated: PGDA=0.8570, PGDc=0.1424 and DP=0.40. It may be regarded as one of the more stable genetic markers. It is of great value that the polymorphism is used for paternity test of first-trimester pregnancy and identificantion.