Abstract: We explored the gas exchange, chlorophyll fluorescence properties and Rubisco activity in Ficus concinna var.subsessilis under high temperature stress. The results showed that with continueing of high temperature, the net photosynthetic rate (Pn) in Ficus concinna was decreased, and the stomatal conductance (Gs) was slightly decreased. The transpiration rate (E) was increased after the 4 d of treatment, and then maintained stable, while the intercellular CO2 concentration (Ci) was rather stable, which indicated that the decreased Pn under high temperature stress was not resulted from the decrease of stomatal conductance. Further studies showed that the efficiency of energy conversion of open PSⅡ (Fv′/ Fm′), the actual efficiency of total PSII centers (ΦPSⅡ), photochemical quenching (qP), and electron transport rate (ETR) was decreased. and the non-photochemical quenching (NPQ) were increased after the 12 d of high temperature stress, and then was slightly decreased. There results suggested that that primary limitation of Pn was suppression of Rubisco activity, thereby the PSII activity and the electron transport were decreased.