Abstract:To enhance benefits of Tilia amurensis man-madel forest, an experiment was carried out to study the rational topdressing rate of N, P and K. using Tilia amurensis ten years age young plantation as the study object. The quadratic regression orthogonal rotation test was adopted in this experiment. The results showed that the optimum combination fertilizers was 97.70g/tree potassium chloride fertilizer +126.47g/tree fused calcium-magnesium phosphate fertilizer +241.90g/tree urea fertilizer. Fertilization could improve net photosynthetic rate and transpiration rate with N fertilization was most significant compared to single application of P and K. N, P and K fertilization has a synergetic effect on the net photosynthetic rate and transpiration rate. The diurnal change trend of net photosynthetic rate was similar to that of transpiration rate, but was divergent on time. The increase of daily net photosynthetic rate was lagged behind compared to that of transpiration rate.