Abstract: oxalamide as expensive slow-release nitrogen fertilizer is gradually known to us, in order to reduce the cost of oxalamide in agriculture application, oxamide mixed with urea is an effective way. The experiment was conducted to obtain optimal oxamide and urea ratio for increasing sweet potato yield in field. Urea and oxalamide are mixed with 5 treatments under the same input of N,P,K: 0:100%, 25%: 75%, 50%: 50%, 75%: 25%, 100%: 0, respectively. The results showed that the increase of oxalamide ratio accompanied with the increase of sweet potato yield, 0:100% trail had the highest yield of sweet potato. 100%: 0 trial had lowest yield of sweet potato. It was suggested that the use of oxalamide can promote sweetpotato yield. During the medium period of sweet potato growth, sweetpotato nitrogen demand was the highest. The soil ammonium nitrogen and nitrate nitrogen content were high and could meet the demand for sweet potato nitrogen fertilizer under 0:100%, 25%: 75%, 50%: 50% trail during the medium period of sweet potato growth. Considering sweetpotato yield, 0:100% trial was the best for sweet potato production. Considering the cost , 50%: 50% trail was the best for sweet potato yield.