In May 1995, the kinetic parameters (V_max and K_m) of alkaline phosphatase in interstitial water, overlying water and surface water were differed significantly in Donghu Lake (Wuhan) and Yanxihu Lake(P<0.05).At Station I and HI of Donghu Lake, V_max values of overlying water were much higher than those of surface water, while in Yanxihu Lake V_max values of overlying water were much lower.At Station II in Donghu Lake, both V_max and K_m values were quite lower in overlying water, exhibiting a higher catalytic efficiency.This phenomenon might relate with the compositions of enzyme activities.In brief, a pronounced downward gradient of enzyme catalytic efficiency was observed in Donghu Lake, which was not recorded in Yanxihu Lake.Consequently, the enzymatic hydrolyzable P may contribute to the internal loading of the eutrophic lake, and stratification of kinetics and compositions of phosphatase in shallow lake is theoretically noticeable.