It has been established that extracellular ATP (eATP) is an important extracellular molecule required to regulate many physiological responses of plants.This study investigates the effects of eATP on the operation of photosystem Ⅱ and the allocation of absorbed light of bean (Phaseolus vulgaris L) leaves under low temperature.The results showed that although low temperature did not have significant effect on the potential maximal photochemical efficiency of PSⅡ(F_v/F_m),low temperature decreased the values of the effective photochemical quantum yield of PSⅡ [Y(Ⅱ)].Further works showed that low temperature decreased the fraction of photochemical efficiency (P) but increased the fraction of antenna heat dissipation (D) and excess energy (E).The level of eATP decreased under low temperature.When the application of exogenous ATP alleviated the decreases of the eATP level under low temperature,the values of Y(Ⅱ) and P were significantly increased,while the values of D and E were decreased.These results indicate that low temperature caused a decrease in the operation of the PSⅡ photochemistry and caused an increase in dissipation of light energy,and eATP could have function in enhancing the performance of PSⅡ photochemistry and decreasing the dissipation of light energy under the condition of low temperature.