Abstract: Effect of varied NPK ratios on the biomass accumulation, nutrient absorption/distribution and quality of sweet potatoes were studied in a field experimentation.During the stage when the tubers and vines were allowed to grow simultaneously, fertilization with complete nutrients (N, P and K) on the sweet potato plants increased the biomasses of the tubers, shoots and leaves, as well as the nutrient contents in the tubers.Shortage on N, P and K was found to be most critical, followed by a lack of N, on the biomass accumulation.N deficiency in the soil affected the N absorption and increased the K assimilations in the tubers, but had no significant effect on the P assimilations of different organs.P deficiency significantly decreased the contents of N and K in the tubers.A deficiency in K raised the N absorption of the tuber, but did not significantly affect the P assimilations of different organs.When NPK were in a short supply, the nutrient content of the tuber was negatively affected.And, the starch content in the tubers was also lower than other deficiency conditions, while N deficiency produced the second lowest starch content in the tubers.However, the difference between N deficient sweet potatoes and P or K deficient counterparts was not significant.The results suggested that, except when N, P and K were all depleted, a shortage on N would affect most on the normal growth and nutrient contents of the sweet potatoes, if the tubers and vines were growing on the plant at the same time.