【Objective】 The purpose of this study was to investigate the effects of nitrogen, phosphorus and potassium fertilization on Catalpa bungei seedling biomass allocation and nutrient use efficiency. 【Method】 Biennial C. bungei seedling clone 1-4 was selected as experimental material, twelve different nitrogen, phosphorus and potassium fertilization treatments were set, and the growth biomass and nutrient use efficiency were determined.【Result and conclusion】 Nitrogen, phosphorus and potassium fertilization had a significant effect on the biomass accumulation and allocation; treatment 10 (12 g·plant^-1 urea,12 g·plant^-1 calcium magnesium phosphate, 12 g·plant^-1 potassium sulfate) had the maximum total biomass［(331.05±5.21) g·plant^-1］, three times of no fertilization（CK）and two times of single nitrogen fertilization of 12 g·plant^-1 (CK₁₂). When fertilization of N and K was fixed, the proportion of seedling root biomass initially increased, then decreased with increasing P fertilization,and the maximum value appeared when 12 g·plant^-1 P fertilization was set. Different treatments had a significant effect on nitrogen, phosphorus and potassium contents of seedling. Treatment 10 was the maximum in nitrogen, phosphorus and potassium contents ［ (5.32±0.17),(0.84±0.07) and (4.89±0.11) g·plant^-1］，which were 5, 6 and 8 times of CK respectively. The maximum nitrogen fertilization efficiency was treatment 10,(57.11±0.94) g·g^-1. Based on comprehensive analyses, the appropriate proportion of nitrogen, phosphorus and potassium fertilization can increase biomass and improve nitrogen, phosphorus and potassium contents and nitrogen use efficiency of C. bungei seedling. Furthermore, potassium significantly affects the root biomass accumulation.