Abstract: This paper analysed the activities of LDH isozymes in the testes of SD rats exposed tofour different cadimium (Cd) concentrations (O. 2. 0. 4. 0. 8 and 1. 6mg/kg) with the methods of verticalstab of polyacrylamic gel electrophoretics and spectrophometrics. The results showed that there wassignificant difference (P0. 05) in the activity of every LDH isozyme between the normal team and eachof four Cd poisoned teams. The activity of LDH -X was the most significantly inhibited among LDHisozymes by Cd. The activities of LDH,, LDH2, LDH,and LDH4 were gradually inhibited by Cd, whereas,that of LDH, increased from 0. 2 to 0. 8mg/kg Cd and decreased in 1. 6mg/kg Cd. The total activity ofLDH isozymes decreased in proportion to Cd effects on three-gene expressions of H, M and C subunits inLDH isozymes.