Abstract: 【Objective】The purpose of the study was to investigate the effects of spraying exogenous chemicals on the energy level of rice spikelets under high temperature stress and its relationship with rice high temperature stress tolerance, in order to provide a theoretical basis for the cultivation of heat resistant rice. 【Method】Common indica rice high temperature tolerant variety GLA15 and high temperature sensitive variety MH101 were used as experimental materials. During meiosis, foliar spraying of clear water was used as a control(CK). Five exogenous substance spraying treatments were applied: 0.15 mmol/L sucrose(Suc), 25 mmol/L acarbose(Aca), 10 mmol/L salicylic acid(SA), 10 mmol/L salicylic acid+0.15 mmol/L sucrose(SA+Suc), and 10 mmol/L salicylic acid+25 mmol/L acarbose(SA+Aca). Immediately after spraying, a sunlight type artificial climate chamber was used for high temperature stress treatment(daily maximum temperature/daily minimum temperature being 38.0 ℃/29.0 ℃). The effects of different exogenous substances on the energy level, pollen vitality, spikelet fertilization rate, sucrose metabolism enzyme activity, antioxidant enzyme activity, carbohydrate content, phenylpropanoid metabolism enzyme activity and secondary metabolite content of spikelets under high temperature stress were analyzed. 【Result】Spraying different exogenous substances could construct different levels of spikelet energy. Compared with CK, under high temperature stress, the ATP content and ATPase activity of the two rice varieties were the highest in SA+Suc treatment and the lowest in Aca treatment. Moreover, the ATP content and ATPase activity of GLA15 spikelets were generally higher than those of MH101. Under high temperature stress, the pollen viability and spikelet fertilization rate of SA+Suc, Suc and SA treatments were all higher than those of CK, while the pollen viability and spikelet fertilization rate of Aca treatment were significantly reduced compared to CK(P<0.05, the same below). The pollen viability and spikelet fertilization rate of MH101 were reduced by 10.3% and 35.6% respectively compared to CK, while GLA15 was reduced by 2.5% and 8.0%, with a decrease of MH101>GLA15. Compared with CK, under high temperature stress, the activities of sucrose synthase, acid invertase, superoxide dismutase, peroxidase, and ascorbic acid peroxidase increased in SA, Suc, and SA+Suc treatments, while the activities of the above enzymes decreased in Aca treatment. The carbohydrate content in the spikelets treated with SA, Suc, and SA+Suc increased, while the carbohydrate content in the spikelets treated with Aca decreased(except for the fructose content and soluble sugar content of MH101). SA could promote the sugar metabolism level of spikelets, thereby alleviating the inhibitory effect of Aca on soluble sugar, sucrose, and non structural carbohydrate contents. Under high temperature stress, the activities of phenylalanine ammonia lyase, cinnamic acid 4-hydroxylation, 4-coumaric acid CoA ligase and lignin content of the two varieties were higher in SA+Suc treatment, while the total phenolic and flavonoid contents were higher in Suc treatment.【Conclusion】Exogenous chemicals mainly affect carbohydrate content and sucrose metabolism, regulate the energy level of spikelets, maintain high antioxidant enzyme activity and secondary metabolite levels, and enhance the tolerance of rice floral organs to high temperature stress. Improving the initial energy level of spikelets through the application of exogenous substances may be a potential technical strategy for effectively alleviating high temperature stress in rice.