Abstract: The net photosynthetic rate (Pn) of Dolichomitriopsis diversiformis(Mitt.) was measured under controlled air temperature (T_a),plant water content (PWC) and irradiance (Photosynthetically Active Radiation,PAR) in laboratory.The results showed that Pn was closely related to PAR,T_a and PWC.The response curve of Pn to PAR was a right angle hyperbola,and the parameters were affected by T_a and PWC.The Pn reduction was great when PWC was low and T_a was high,or when PWC was high and T_a was low.The peak Pn (P_max) was observed underweak light (PAR<200 μmol·s^-1·m^-2) and relatively low (50%～80%) PWC.Under higher T_a,P_max was higher,but decreased when T_a was higher than 25 ℃.The PWC range within which P_max occurred increased in accordance with the increase of PAR.When PAR was lower than 200 μmol·s^-1·m^-2,the T_a range within which P_max occurred was relatively high (20～25 ℃),and P_max increased with the increase of PWC.When PWC was higher than 80%,P_max decreased with the increase of PWC.The T_a range within which P_max occurred decreased in accordance with the increase of PAR.Under moderate light (230<PAR<270 μmol·s^-1·m^-2),the sensitivity of Pn response to T_a and PWC was higher than that under higher or lower light.The Pn response to T_a and PWC was saddle-like,and its parameters were altered according to the variation in PAR.