Abstract: Polyaspartic acid（PASP）is an environment-friendly polymeric substance that has been frequentlyused as fertilizer synergist and sustained release agent in agriculture. In order to investigate the effects of PASPon nitrogen uptake and utilization in poplar seedlings,12 gradient treatments of different concentrations ofnitrogen and PASP were set in the hydroponic-grown poplar hybrid ’Nanlin 895’seedlings. The results showedthat the addition of PASP in nutrient solution had an obvious promoting effect on poplar growth and developmentwhen nitrogen supply was inadequate,and it improved the plant height,number of leaves and shoot biomassand the utilization efficiency of nitrogen,whereas the root to shoot ratio and nitrate concentration in seedlingswas decreased. However,the exogenous supplement of PASP aggravated the stress of high nitrogen under thecondition of high nitrogen. The results demonstrated that PASP could be used as fertilizer synergist for poplar,and the appropriate addition of PASP under insufficient nitrogen conditions would promote growth performanceof poplar seedlings.