Abstract: By means of guadratic rotational combination design, a three-factor (N.P.K) experiment was conducted in a plastic greenhouse. With the aid of computer, guadratic regression models demonstrating the relationship between N.P.K and yielel were established. The effect of N.P.K on sweet pepper, its marginal effect and interactions were studied. The result indicated that N had bigger effect on yiecel formation of sweet pepper. The optimum compound also was discussed.