Abstract: The experiment was conducted in Xiangshan,Zhongwei,in Ningxia in 2009.Effects of water, organic fertilizer and density on pepper yield in sandy field were studied through 311-A application of optimal fitting saturated regressive design.The results showed that the effect of single factors on the yield was：Organic fertilizer〉water〉density; the effect of interaction two-factor on yield was：water＋density〉water＋organic fertilizer？organic fertilizer＋density.The results after simulated optimization showed the optimal combination of water,fertilizer and density was that the supplementary water was 6m^3/667m^2,fertilizer amount was 114kg/ 667m^2 and planting density was 4000plant/667m^2.The yield was 1582.12kg/667m^2.