Abstract: Availabilities of calcium and phosphorus in nutritive salts for grass carp, as determined by the chromic oxide indicator method, were as follows: (Ⅰ) availabilities of calcium: 81.3% in calcium lactate, 26.4% in calcium carbonate, 69.7% in monobasic calcium phosphate, 39.9% in dibasic calcium phosphate, and O in tribasic calcium phosphate; (2) availabilities of phosphorus: 90.3% in monobasic sodium phosphate, 90.3% in monobasic calcium phosphate, 60.3% in dibasic calcium phosphate, and 2.8% in tribasic calcium phosphate. The results of the experiment indicated that the availabilities of Ca and P were directly proportionate to the solubility of nutritive salts. Availabilities of calcium, phosphorus, magnesium, and iron contained in anchovy fish meal, dehulled soybean meal, peanut meal, ground corn and wheat middlings were also studied. Results showed that magnesium and phosphorus in the natural feeds could be utilized effectively by grass carp, but iron and calcium could scarcely be absorbed. Thus, in order to satisfy the mineral needs for the growth of grass carp, calcium and iron should be added to the diet.