Abstract: It is studied on photosynthetic characteristics of four different heat-tolerance capsicums in alimentation growth periods by CI-301PS CO2 GAS ANALYZER, for probing into the relation between photosynthetic parameter and capsicum heat-tolerance. The results showed that heat tolerance of different peppers was related with photosynthetic characteristics, such as net photosynthetic rate (P), transpiration rate(E), stomatal conductance(C), and net photosynthetic rate, transpiration rate and stomatal conductance of heat-tolerance pepper were higher than these of non-heat-tolerance pepper during the midday depression.