Abstract: Field experiments were conducted at the station of Shunyi Agriculture Sciences Institute in Beijing. This study is about the effects of 5 levels of nitrogen applying on dry matter accumulation and N, P and K absorption efficiencies of sweet potato. It is indicated that yield reached the highest value of 30.4 t/hm2 at N level of 210 kg/ hm2, and the corresponding dry matter reached 21423 kg/hm2 and the P and K accumulations reached the highest values of 145.7 kg/hm2 and 247.4 kg/hm2. When the N level exceeded 210 kg/hm2, dry matter did not increase with the increase of N applying which showed a platform relationship. We can conclude that 210 kg/hm2 N was the optimum N level for sweet potato.