Effects of different fertilization proportions of N and P on dry-land wheat yield in gully region of the Loess Plateau in the condition of normal rainfall were studied based on the long-term experiment in Changwu, Shaanxi Province. A trend surface model of dry-land wheat yield in the gully regions was constructed using trend surface analysis. Fertilization proportions for higher wheat yield were found and the fertilization proportions for the highest yield were N=178.169 kg/hm² and P=198.405 kg/hm². The maximum wheat yield was 6 152.6 kg/hm². Wheat yield with different N and P proportions in the condition of normal rainfall can be predicted by the trend surface model, which provides a theoretical basis for the actual agricultural production.