Larix principis－rupprechtii Mayr. is one of the most proper conifer species of conifer for forestation in north China. Seed orchards of Larix principis－rupprechtii Mayr. have been built since 1960s in China, and some of which have already contained three generations. However, lack knowledge of variations of genetic variationsdiversity after selection on molecular level causes some unclearness in breeding and forestation. 10 EST-SSR primers are used in this study to analysis the genetic diversity among three generations in the seed orchard in Hebei. Each primer has 2-5 loci. The numbers of average effective loci for the 1st, 2nd, and 3rd generations are 1.92, 1.81, 2.07. Shannon index are 0.7127, 0.7052, 0.7908. Heterozygote excesses in the population. The value of Fst is low, which shows that Genetic differences are mainly occurred in one generation rather than between generations.