It is difficult to distinguish the gynogenetic fish from common one by morphology and physiology of grass carp(Ctenopharyngodon idella).To establish a molecular method of distinguishing the two groups,an artificially induced gynogenetic grass carp group was produced by activating grass carp eggs by the ultraviolet light(UV)irradiated common carp(Cyprinus carpio)sperm and subsequently blocking the release of the second polar body(PB2).Eight microsallite markers were detected,among which five markers were selected to establish a microsatellite identification method.33 alleles were amplified on 8 loci.The average value of observed homozygosity and polymorphism information content(PIC)were 0.203 1 and 0.552 8 in the common group,and those were 0.716 1 and 0.357 2 in the gynogenetic group,respectively.The genetic similarity between the two groups was 0.873 3.And then five microsatellite markers were used for genetic identification of gynogenetic grass carp.The total numbers of alleles at these five loci were between 5 and 7 for 48 gynogenetic grass carp,while those were between 8 and 10 for 48 common grass carp.So we can completely distinguish the two groups of grass carp according to the number of alleles amplified at the five loci.The probability of identification of the gynogenetic grass carp reached 99.92%,premised on the theory of probability calculation.In conclusion,the genetic homozygosity in the gynogenetic group was much higher than that in the common group,and therefore the gynogenesis technique was an effective method to quickly establish pure line and fix merits.Using polymorphic microsatellite markers can distinguish gynogenetic group(or highly inbred population)from common group according to the variation of genetic homozygosity.