Abstract: The protease activities of both the intestine and the hepatopancreas raised with increasing protein levels when grass carp was fed on the diets containing proteins 32% to 40%. Protease activity in the hepatopancreas was higher than in the intestine. The protease specific activity in hepatopancreas of grass carp fed on grasses was measured to be per mg protease protien per minute producing 332.5 μg tyrosines and in intestine being 260.0μg tyrosines. The protease optimal activity of intestine and hepatopancreas have been found at pH 6.5 and pH 7.0 using casein as substrate and pH 4.0-9.0 of buffers. The intestine and hepatopancreas proteases acted optimally at 166.67μg/ml and 208.3μg/ml of casein concentrations under the casein concentration range of 83.3μg/ml to 333.3μg/ml.The protease activity in hind intestine was found to be highest and those in fore and in middle intestine were less.