Abstract: The development of germ cells also exist the cell cycle control.It is not known whether the mechanism of cell control of germ cells is as same as culture cells.To known it,a study on the expression of PCNA,cdc2,cyclin D1,p21 and p16 gene in germ cells of testis and ovary of maturation(more than 10 weeks old)Kunming mice was carried by using in situ hybridization technique with Dig Labeled DNA probe.The results shown:PCNA gene expressed mainly in spermatocysts and spermatocytes of testis of the mice,but not in ovary cells;cdc2 gene, cyclin D1 gene,p16 gene and p21 gene were not expressed in the cells of testis or ovary.These facts suggest that the genes controlling cell proliferation and differentiation in germ cells don’t act in germ cells as same as they act in culture cells,in another word,the mechanism of cell cycle control of germ cells is different from that of culture cells.