Abstract: In order to study the effect of different nitrogen supply forms on leaf photosynthetic characteristics, root yield and quality of sweetpotato, a pot experiment was conducted with three nitrogen forms, NH+4-N［(NH4)2SO4)］, NO-3-N(NaNO3) and CONH4-N(urea) using sweetpotato cv. Xushu18. The results showed the chlorophyll contents(CCI) with CONH4-N were the highest after 30 d and 50 d of planting, while CCI with the NH+4-N was the highest in 70 d. The photosynthetic rate and photosynthetically active radiation(PAR) under the NH+4-N treatment are the highest. TheNO-3-N treatment could promote more photosynthesis of sweetpotato leaves, and the yield under the NH+4-N treatment is higher than those of the NO-3-N and CONH4-N treatments, increased by 10.6% and 17.2%, respectively. There are significant differences(P0.05) between the NH+4-N treatment and other treatments. Meanwhile, the starch content and protein content of sweetpotato roots under theNH+4-N treatment are the highest, while the soluble sugar content and reducing sugar content under the CONH+4-N treatment are the highest. The NH+4-N treatment promotes the values of peak viscosity, breakdown and consistence of sweetpotato starch, and theNO-3-N treatment promotes the values of through viscosity and final viscosity.