Abstract: The effects of Cu2+ and Pb2+ (single factor and joint toxicity) attack on DNA damages in loach oosytes with different concentration of Cu2+(0.01, 0.10 and 0.25 mg/L respectively)and Pb2+(0.05, 0.50 and 0.75mg/L respectively), and Cu2++Pb2+(0.01 mg/L+0.05mg/L, 0.10 mg/L+0.50 mg/L and 0.25 mg/L+0.75 mg/L respectively)were studied by means of in door exposure and with the technique of SCGE. The results showed that the DNA damages in loach oosytes by single factor Cu2+ or Pb2+showed significant differences with dose-effect and time-effect (P0.05). As for joint attack of Cu2++Pb2, it showed that there were significant differences with dose-effect and time-effect under 5d exposure (P0.05), but it seemed to be an antagonism within 5d to 10d exposure. The results of the study showed that both single factor or joint attack by heavy metals will cause DNA damages to loach oosytes. Meanwhile, the genetic toxicity effects appears.