In the study, the gas exchange parameters and chlorophyll contents in the needles of Pinus koraiensis Sieb. et Zucc. exposed to exogenous nitric oxide (NO) were determined. The Pinus koraiensis Sieb. et Zucc. seedlings were treated with sodium nitroprusside (SNP), a NO donor, at 5 different concentrations ranging from 0 mM to 1 mM. The result showed that at different concentrations exogenous NO had different effects on the photosynthetic parameters and photosynthetic pigments. The content of chlorophyll was maximal in the treatment with SNP at 0.01 mM. At low concentrations (0.1 mM) SNP significantly increased the photosynthetic rate (PN) and decreased the Respiration rate (RD) and Compensation irradiance (IC) of the needles (p<0.05). The experiment proved that at low concentrations exogenous NO signals increased the photosynthesis of Pinus koraiensis Sieb. et Zucc. seedlings. The present results suggested that the lower concentrations SNP might decrease the level of reactive oxygen species (ROS) and promote the growth of the Pinus koraiensis Sieb. et Zucc.