Abstract: Light compensation point,saturation light intensity,CO2 compensation point carbozylation efficiency and the effect of temperature and humidity on the photosynthetic rate of Paris polyphyllavar.yunnanensiswere studied with the photosynthesis analysis system and in the phytotron.It shown light compensation point,CO2 compensation point and carbozylation efficiency was 5.7μmol/(m2·s),65μmol/mol and 0.0295 respectively,but the saturation light intensity was not monitored even if the photosynthetic active radiation increased from 0 to 2000μmol/(m2·s) and the optimal radiation was from 750 to 2000μmol/(m2·s).The net photosynthetic rate increased with CO2 concentration increasing,the CO2 concentration over normality would enhance utilization efficiency of light energy in photosynthesis.When the leaf temperature increased from 11℃ to 20℃ the net photosynthetic rate increased,but it increased from 20℃to 35℃,the rate decreased.The optimal temperature was from 16℃ to 28℃.When relative humidity went up from 20% to 85%,the net photosynthetic rate increased.The optimal humidity was above 75%.