Abstract: In order to study biochemical toxicity effects of cadmium on testis,different doses of cadmium chloride(0.2,0.4,0.8mg Cd/kg body weight)were administrated ip to the adult male Sprague-Dawley rats.After 7 days,the activities of enzymes in testis and testicular sperm head counts and daily sperm production were observed.The result showed the activities of alkaline phosphatases (ALP)and lactate dehydrogenase isozyme-X(LDH-X)decreased in the middle and high dose groups singificantly.But activities of other enzymes such as acid phosphatases(ACP),lactate dehydrogenase isozyme(LDH),glucose-6-phosphate-dehydrogenase(G-6-PDH),sorbitol deydrogenase(SDH),testicular sperm head counts and daily sperm production decreased in the high dose group only. These results suggest cadmium toxicity on male reproductive system is associated to activities of testicular enzymes.ALP and LDH-X are sensitive biochemical endpoints reflecting cadmium toxicity on male reproductive system.