Abstract: To investigate the effects of heavy metals (copper and cadmium) on Oryzias melastigma, the relationships among indicators were analyzed. Three concentration gradients of copper and cadmium were used according to the seawater quality standard, and five physiological and biochemical indicators lactic acid (LA), lactate dehydrogenase (LDH), testosterone (T), follicle stimulating hormone (FSH), luteinizing hormone (LH) and fecundity were determined. The LA content of O. melastigma decreased significantly with the prolongation of copper exposure time, and increased with the increase of cadmium concentration. The activity of LDH did not change much under copper poisoning, but increased slightly with the prolongation of cadmium exposure time. The content of T increased with short-term copper treatment, but it decreased significantly with the prolongation of the time. The content of T increased with the enhanced cadmium toxic concentration and prolonged time. The content of FSH and LH decreased significantly with the increase of copper poisoning, and decreased with the increase of cadmium concentration, and the contents of both FSH and LH were closely related to T change. The fecundity of O. melastigm showed a significant downward trend with the prolongation of copper exposure time and the increased concentration. These results indicated that copper and cadmium poisoning could cause physiological and biochemical changes of O. melastigm with a pattern of gender differences, and that female fish can be selected for related pollution monitoring.