Abstract: Taking 15 grape rootstocks as experimental materials,chlorophyll fluorescence parameters was measured under high temperature.The effects of high temperature on net photosynthetic rate and chlorophyll fluorescence parameters of 15 grape rootstocks were investigated,in order to provide a reference for the grafting cultivation of grape.The results showed that the hot weather is concentrated in late July and early August in shanshan in 2020,the temperature above 40 ℃ can be as long as 7 hours.Leaf relative water content and relative conductivity were decreased,net photosynthetic rate of R4,R5,R8 and R9 changed as a single peak curve and others showed a-double peak,the big peak is in the morning and the small peak is in the afternoon,the hump was appeated at 14:00 or 16:00,there′s a midday depression of photosynthesis,Fo was increased,accompanied by temperature increased and Fo was no long changed when temperature above 40 ℃,diurnal fluctuation of Fm、Fv/Fo、Fv/Fm was ‘U’.Fuzzy membership function analysis was used to analysis Fo、Fm、Fv/Fo、Fv/Fm and sort the composite value,R11 was number 1,the next was R18,R7,R2,R5,R8,R4,R16,R6,R10,R19,R3,R1,R13,R9 in turn.