The respiration and excretion rates of Meretrix meretrix at different salinities were studied at 20°C in laboratory in December 2008. 1) It was shown that the effects of salinity on oxygen consumption rate(OR) and ammonia excretion rate(NR) in Meretrix meretrix are extremely significant(pÃ0.05), when salinity changes from 8.2 to 28.1. 2) At the same time, the trend of ratio of O/N shows first increased and then decreased with the raise of salinity, moreover, and the ratio O/ N of the largest is 11.38 at 28.1.