The autophagy-related gene CsATG3b was cloned from tea trees and its function in nitrogen utilization was verified in Arabidopsis thaliana to explore the potential role of CsATG3b in nitrogen utilization in tea trees.The results showed that the expression level of CsATG3b in tea leaves increased with the increase of tea leaves maturity.Compared with wild-type Arabidopsis （WT），the root to shoot ratio and content of nitrogen in CsATG3b overexpressing （CsATG3b-OE） lines under low nitrogen were significantly increased.Overexpression of CsATG3b changed the distribution of nitrogen within the plant.It promoted the distribution of nitrogen to stems under normal nitrogen，while it promoted the distribution of nitrogen to roots under low nitrogen.The CsATG3b overexpressing （CsATG3b-OE） lines significantly upregulated the expression levels of nitrogen absorption and transport related genes AtNRT1.1，AtNRT2.1，AtNRT2.2 in roots，amino acid transport genes AtAAP1，AtAAP4，AtAAP6 and autophagy related genes AtATG3，AtATG5，and AtATG8b in rosette-leaves under low nitrogen.The CsATG3b overexpressing （CsATG3b-OE） lines increased nitrogen accumulation under normal nitrogen and significantly improved nitrogen utilization efficiency under low nitrogen.It is indicated that the overexpression of CsATG3b can improve nitrogen utilization efficiency and tolerance to low nitrogen in Arabidopsis by regulating the expression of nitrogen absorption and transport genes and autophagy related genes.