Abstract:Machilus pauhoi is a typical subtropical precious timber and economical tree species. In order to provide scientific basis for the introduce of Machilus pauhoi in Zhejiang province, the effects of simulated acid rain (SAR) on its growth and photosynthesis were measured. The results showed that plant height distinctly reduced by pH2.5, but no significant impact on height, ground diameter and chlorophyll at pH4.0. SAR (pH 4.0) has ho significont effect on photosynthetic mdexs, while SAR (pH 2.5) improved the intercellular CO2 concentration(Ci), the dark respiration rates(Rd) and light compensation point (LCP),increased stomatal conductance (Gs) and transpiration rate (Tr),resulting in that the maximum net photosynthesis（Amax） of Machilus pauhoi was significant lower. The result revealved the sensitivity of Machilus pauhoi to acid rain enhanced environment through correlation and regression analysis.