The annual cycle of reproductive organs in a wild population of a Tibetan frog, Nanorana parkeri, was studied. For females we used the pigmentation and size of the ovarian follicles to designate the reproductive conditions. Males were analyzed according to their spermatogenic stages using histological sections of their testes. The results showed that each sex had a seasonal reproductive cycle. However, females reproduced biennially or more, while males bred annually. We presumed that the sexual differences in reproductive investment contributed to the annual reproductive cycle difference between the sexes of N. parkeri. Moreover, this species did not have the post-breeding resting period, which was confirmed by the fact of reinitiation of spermatogenesis shortly after breeding.