Abstract: The effects of nitrogen (N), phosphorus (P) and potassium (K) on yield and quality of tomato were studied with the design of three factors and quadratic saturation Doptimal regression (310). According to the data obtained, a mathematical model was developed, in which N, P and K were independent variables and tomato yield and quality parameters were dependent variables. The model analysis shows that yields and quality of tomato are significantly influenced under the N, P and K applications, and there are significant interactive effects between every two factors. Among the three factors, K has the greatest effects on yield and quality of tomato. At the lower levels, the yields and quality are improved along with the increase of N, P and K, and are decreased when N, P and K are applied too much. Obtained by computer simulation in this experiment, the yields could reach to 150 t/ha and quality grade could pass 95 when the fertilizer rates are N 520.2-758.4 kg/ha, P2O5 294.8-367.3 kg/ha and K2O 1051.5-1299.8 kg/ha. The suitable ratio of N∶P2O5∶K2O is about 1∶0.52∶1.84.