Optimizing the amount of water and nitrogen is the main way to increase crop yield and improve crop quality. Sweet potato, rich in anthocyanins, carotenoids and other health-care nutrients, has a good prospect for starch processing and is an important food and energy crop. Nitrogen is a necessary macronutrient element for sweet potato growth and development. Soil moisture is an important factor affecting soil nitrogen distribution in the field and sweet potato growth. Proper soil moisture can promote sweet potato vines growth and increase sweet potato yield. Meanwhile, soil moisture can help give full play to nitrogen fertilizer effect. Different soil wetted percentages and nitrogen fertilizations have different effects on sweet potato yield, water and fertilizer use efficiency, and sweet potato quality. The experiment was conducted in Rizhao City, Shandong Province from May to October 2020. The effects of different soil wetted percentages and nitrogen fertilizations on sweet potato vines growth, yield and quality under drip irrigation with black plastic film mulching were studied. The sweet potato vine stem diameter, vine length, and dry matter quality were measured throughout the whole growth season. The potato yield, tuber grade, starch, crude protein, soluble sugar and total carotenoid content were measured. The results showed that non-irrigation treatment could not fully exert the effect of nitrogen fertilizer, and caused drought stress, which was not conducive to the growth of sweet potato vines and dry matter accumulation. High nitrogen fertilization (N3) treatment improved the above-ground growth and made the sink-source imbalance. Then it inhibited the underground dry matter accumulation. The P2 treatment provided appropriate water conditions for sweet potato growth and promoted nitrogen absorption of sweet potato, which was beneficial to underground dry matter accumulation. Under the same soil wetted percentage treatments, the number of sweet potato per plant and the quantity (mass) of large potato pieces would first increase and then decrease with nitrogen fertilization increase. Irrigation increase can increase sweet potato yield. Nitrogen fertilization significantly increased sweet potato yield and the quantity (mass) of large sweet potato pieces. However, excessive nitrogen fertilization reduced sweet potato yield and the quantity (mass) of large potato pieces. Excessive soil nitrogen content inhibited sweet potato soluble sugar accumulation, while higher soil water content alleviated the inhibitory effect of high nitrogen on tuber soluble sugar accumulation. Sweet potato tuber total carotenoid content was decreased with the increase of nitrogen fertilization, and the rate was slowed down with the increase of nitrogen fertilization. Higher nitrogen fertilization promoted sweet potato formation tuber crude protein. Considering the yield and quality and partial factor productivity（PFP）of sweet potato, the suitable soil wetted percentage for sweet potato in Shandong Province was 60%, and the nitrogen fertilizer amount was 180.25kg/hm2.