It was systematically studied for over 2 years on pisciculture usingammonium chloride as nitrogen source in polycultured ponds. Under same condi-tion, six manuring treatments with different chemical fertilizer and N/P ratio in1989 and four treatments in 1990 were carried out in polucultured ponds wheresilver carp (Hypophthalmichthys molitrix) and bighead (Aristichthys nobilis) werereared as main objects. The effects of ammonium chloride on the physi-chemicalcharacteristics of pond water, nutrients, primary productions, species and biomassof phyto-- and zooplankton in ponds, and their periodic changes before and aftermanuring under 4 temperature ranges of below (but not) 20℃, 20 to 25℃, 25 to30℃ and over 30℃, and their seasonal changes were studied and camparied withother nitrogen sources. Also the chemistry of bottom silt in ponds, the biochemicalcomponents of blood, nutritional contents and amino acid and fatty acid compo-nents of the muscle of silver carp and bighead, the yield of both fishes and theeconomic banefits of pond culture were studied and investigated.