Abstract: Capsicum annuum L.‘Niuneimu Huangshuai’used as experimental material，the possible mechanism of foliar-spraying 1-methylcyclopropene（1-MCP）alleviating the injury of pepper seedlings under high temperature stress was studied. The results showed that the growth of pepper seedlings was significantly suppressed by high temperature stress，and the heat injury index was reached up to 60.5. The biomass，root activity，chlorophyll content，net photosynthetic rate，leaf antioxidant enzymes activities，the contents of soluble protein and soluble sugar of pepper seedlings were significantly promoted by foliar-spraying 80 g · hm-2 1-MCP compared with the treatment of foliar-spraying water. Moreover，the accumulation of reactive oxygen species and cell membrane permeability of pepper seedlings treated with foliar-spraying 80 g · hm-2 1-MCP under high temperature were significantly decreased compared with the treatment of foliar-spraying water. In addition，the abscisic acid content and ethylene release rate in pepper leaves treated with 1-MCP under high temperature stress was decreased，on the contrary，fruit setting and yield per plant were effectively improved compared with the treatment of foliar-spraying water. In conclusion，the results indicated that foliar-applied suitable concentration of 1-MCP on pepper seedlings under high temperature stress could enhance photosynthesis rate and osmotic adjustment activity，inhibited the accumulation of reactive oxygen species，and regulate the hormone contents，as a result，improved the yield of peppers.

Key words: Capsicum annuum, 1-MCP, high temperature stress, reactive oxygen species, yield