The activities of proteinase and amylase can be affected by and can respond to the diet the prawn fed in about 5-8 days. The ratio of specific activity of proteinase to that of amylase is directly proportional to the protein content and inversely proportional to the starch content in the diet. The activities of proteinase and amylase of the prawn fed with a diet containing more protein and less starch (fresh fishes 20%, fish meal 80%) are greater than those of the prawn fed with diets containing less protein and more starch (sweet potato flour over 20%) when six diets were used with different fish meal and sweet potato flour ratio in the culture of the prawn.