In this study, the influence of water temperature and salinity on sand ejection of Manila clams, Ruditapes philippinarum, was investigated. The result showed that, under different water temperature, the highest quantity of sand ejection was at $20^{circ}C$, the value of which was 0.091 g, while the smallest one was only 0.058 g at 0$^{circ}C$. The highest releasing rate, 95.79%, could be seen in $20^{circ}C$ group, while $0^{circ}C$ group was the lowest one, 85.29%. Under different salinity, 30 psu group had the highest value, 0.057 g, and 0 psu (freshwater) group was the lowest one, only 0.026 g. At the same time, the highest releasing rate appeared at 25 psu, which was 90%. 0 psu group was the lowest one in releasing rate, 60.47%. According to these results, we recommend that the clams should be placed into the clear seawater with about 25 psu of salinity at near $20^{circ}C$ to let the clams perform the self-depuration. Better quality of clams containing less impurity in the aquaculture and commerce could be obtained from this pre-treatment.