Experimental cryptorchidism is a common model for examining the expression and function of heat-sensitive spermatogenesis-related genes in testis. Previous studies have shown that germ cells in cryptorchid testis die mainly in an apoptotic way. The molecular mechanism, however, is still unclear. We have established unilateral cryptorchid monkey model (Cynomolgus Macaque) to identify possible molecules involved in the germ cell apoptosis. The degree of germ cell apoptosis, the morphology of the cryptorchid testis, and the changes in the serum concentration of FSH, LH and testosterone after cryptorchid surgery were analyzed. Sertoli cell marker molecule vimentin, the orphan receptor LRH-1, as well as the mitochondria-related protein HSP60 and Bcl-2 were examined. Our results showed that the weight of the cryptorchid testis decreased in a time-dependent manner started from day 7 after the surgery, while the weight of the scrotal testis had no obvious change. HE staining showed that from day 5, some germ cells were detached from the epithelium. A massive degeneration of the seminiferous epithelium characteristic of epithelial structural disorganization and the formation of multinucleated giant cells as well as vacuoles was observed on day 10 and 15. The cryptorchidism induced a marked germ cell apoptosis on day 3 after the operation, reaching a peak level on day 7.