Abstract: Study on different generations of slash pine net photosynthetic rate and its value to the process of nitrogen and phosphorus nutrition of the response pattern using the LI - 6400 portable photosynthesis system.The results showed that net photosynthetic rate of seedling had significant differences in the second-generation seed orchard , first-generation seed orchard and seed stands. Through genetic improvement net photosynthetic rate values of seedling from second-generation seed orchard and the first-generation seed orchard were lower than a generation of its increased 51.29% and 9.82 %; Nutrition instead of nitrogen and phosphorus excessive makes the ribulose-1, 5-bisphosphate carboxylase enzyme activity in leaves lower, thus decreased the net photosynthetic rate value of slash pine. However,the proper amount of nitrogen, phosphorus nutrition can significantly improve the slash pine net photosynthetic rate value and its net photosynthetic rate higher than the control increase 70.31 %and 68.89 %.The second-generation seeds orchard, first-generation seed orchard and seed stands of pot slash pine net photosynthetic rate responding to the different levels of nitrogen nutrition in diurnal process exhibits a double peak type, first-generation seed orchard and seed stands of pot slash pine net photosynthetic rate responding to the different levels of phosphorus nutrition in the diurnal process exhibits a double peak type,but second-generation seeds orchard of pot slash pine net photosynthetic rate responding to the different levels of phosphorus nutrition in the process exhibits two models.