In order to investigate the effects of adding polyasparticacid(PASP)on soil nitrogen leaching loss and nitrogenutilization of tobaccoplants，soil column leaching test with different PASP addition ratio and pot experiment with PASPaddition under different nitrogen fertilizer gradients were set up to study the effects of PASP on soil mineral nitrogenleaching，tobacco plant growth，chlorophyll content，photosynthetic rate，key enzyme activity of carbon and nitrogen metabolism， chemical composition and nitrogen utilization rate. The results showed that adding PASP reduced the leaching loss of nitratenitrogen and ammonium nitrogen in soil，and the greater the proportion of PASPadded，the better the leaching loss reductioneffect. Compared with the controlgroup，under conventional nitrogen application and 10% nitrogen reductionconditions，adding PASP improved the growth of tobacco plants，increased the net photosyntheticrate，enhanced the activity ofkey enzymes in carbon and nitrogen metabolism and root activity，increased dry matter and nitrogen accumulation，andincreased the nitrogen utilization rate by 57.74% and42.54%，respectively. The tobacco plant growth of PASP treated with20% nitrogen reduction was slightly weaker，except sucrose synthase (synthesis direction) activity，other physiologicalindexes were slightly decreased on thewhole，total nitrogen and sugar contents weredecreased，nitrogen accumulation wasdecreased，and nitrogen utilization rate was similar to that of the control group. It was concluded that the application of 5% PASP under the condition of 10% nitrogen reduction could reduce the soil nitrogen leaching loss and increase the nitrogen utilization rate of tobacco plants.