The aim of this paper is to investigate the toxic influence of cadmium on the histopathological alterations of gill and hepatic cells in Tegillarca granosa exposed to various concentrations of cadmium(5 μg/L, 15 μg/L, 45 μg/L, 90 μg/L). The experiment lasted for 96 hours. The results are as follows: as the metal concentration rose, the gill cavity swelled, in which stored lots of haemocytes; finally the gill broke and dissolved, where the epithelia cells dropped; the findings of ultrastructure showed that there was granular osmiophilic material in gill epithelia cells, moreover, the number of secondary lysosome and mitochondrion increased, and the cells became vacuolated. The influnce of cadmium on the microstructure of hepatic cells was not obvious, only turning up some yellow sediment. However, its ultrastructure results indicated that the granular osmiophilic material was also present, and the secondary lysosome increased as well, consistent with the cases in gill; Furthermore, the nucleus of hepatic cells deformed and shrank, even showed vacuoles, suggesting the cells were irreversibly damaged. But the two most sensitive organelle, mitochondrion and endoplasmic reticulum, were normal, so we infer that the results may be caused by antioxidant enzymes, which were induced by cadmium.