Abstract: The planarian Dugesia japonica has a very wide distribution throughout fresh water body in China,especially in mountain streams.Because of the advantages of easy laboratory culture and fast asexual reproduction rate,Dugesia japonica is generally used as an experimental animal for cell biology, reproductive biology and stem cell as well as animal regeneration research. pH is one of the important factor affecting population dynamics,reproductive and other life activities of aquatic organisms,and is also the basic laboratory culture condition of planarian. However,there were no reports about the effect of pH on planarin asexual reproduction and population dynamics. The purpose of the present study was to make certain appropriate pH value for large-scale laboratory cultivation of the planarian. In addition,the study can provide the first-hand information for the in depth research about planarian adaptability to the environment.