Based on the reproductive cycle of Rhodeus uyekii, the reproductive control mechanism was examined under the several combinations of photoperiod and temperature regimes at different phases of their reproductive cycle. In early spring, the gonads developed rapidly under the warm temperature condition(above $8^{circ}C$), regardless of the photoperiod. In late spring or early summer, gonads intensely regressed under the high temperature condition(above $24^{circ}C$), regardless of the photoperiod. Thus, it is concluded that the spawning period of R. uyekii is initiated by the rising of water temperature in spring and is terminated by the high temperature in early summer. In autumn, the gonadal recrudescence occurs under the conditions of artificial long daylength with warm temperature(15L/9D, $12^{circ}C{sim}20^{circ}C$), whereas the gonads remain in the existing condition under the short daylength. Therefore, in autumn the gonadal recrudescence is prevented by the short daylength although the temperature is still in favorable condition. In bitterling, the responsiveness of the gonads to photoperiod varies clearly with seasons, which was declined during the winter but increased during the autumn. The critical photoperiod for maturation ranges 12~13 hours of light per day. The results indicate that the proper ranges of temperature and photoperiod for gonadal maturation of this species are from $8^{circ}C$ to $8^{circ}C$</TEX> and from 13L to 15L, respectively.