Abstract: The factors of photosynthetic physiological ecology of Cryptocarya chinensis were measured with Li-6400 portable photosynthesis system under natural condition and control of irradiance,leaf temperature and CO2 concentration at tropical montane rain forest in Jianfengling,Hainan Island,during the dry season in 2001. The net photosynthesis Pn of leaves in the canopy did not vary much and it had the characteristics of low light saturation point (800 μmol·m-2 ·s-1),light compensation point (LCP was between 15 and 20 μmol·m-2 ·s-1) and the maximal photosynthetic rate (A max was less than 7　μmol CO2·m-2 ·s-1). The leaf photosynthesis could respond rapidly to the sunfleck but which lacked the adaptive responses when the high irradiance changed. The short-term response of Cryptocarya chinensis to enriched CO2 concentration could evidently increased the photosynthesis,however,the　stomatic conductance and transpiration would be inhibited. Temperature response of photosynthesis showed that the net photosynthetic rate could be increased by 1. 6　times when air temperature was increased by 4 ℃ among the suitable growing temperatures,but beyond that photosynthesis would be inhibited. There was no evident correlativity between photosynthesis and leaf temperature,irradiance,CO2 concentration and leaf conductance under natural growing conditions,but conic correlativity exists when the growing conditions were controlled.