In the study, the gas exchange parameters and chlorophyll contents of the leaves of Taxus chinensis var. mairei exposed to exogenous nitric oxide (NO) were determined. The seedlings were treated with sodium nitroprusside (SNP), a NO donor, at 5 different concentrations ranging from 0 mM to 1 mM. The experiment was conducted under controlled conditions in laboratory. The result showed that the 1 mM SNP increased the net photosynthetic rate (PN) of Taxus chinensis var. mairei slightly; however, other SNP treatments decreased PN. The water use efficiency (WUE) was increased by exogenous NO, while the stomata conductance (Gs) and the transpiration rate (E) were decreased. The concentrations of chlorophyll a, chlorophyll b, carotenoid and total chlorophyll exhibited 0.1 mM> 0.01 mM> 1 mM > 0 mM > 0.5 mM after 10 days of SNP treatments. The experiment proved that at suitable concentrations of exogenous NO signals increased the photosynthesis, and suggested that the SNP treatment might promote the growth of the Taxus chinensis var. mairei seedlings.