[Objective] T his study aimed to investigate the effects of H_2O_2 and NO on flower development and AP1 gene expression of off-season longan. [Method] N ine-year-old off-season Chuliang longan was sprayed with enhancers and blockers of H_2O_2 and NO to analyze dynamic changes of flower development and AP1 expression. [Result] T he expression level of AP1 gene in off-season longan was improved during flower development. SNP and MV treatments up-regulated the expression level of AP1 gene in leaves and terminal buds to varying degrees during lateral primordium formation. Especially,SNP treatment exhibited the most remarkable effect. DMTU treatment significantly inhibited the expression of AP1 gene in leaves and terminal buds during lateral primordium formation. L-NNA treatment slightly inhibited the expression of AP1 gene in leaves and exerted no significant effect on expression of AP1 gene in terminal buds. [Conclusion]It can be speculated that the enhancement of NO and H_2O_2 signals is conducive to flower development of off-season longan,while blocking H_2O_2 signals may inhibit flower development of off-season longan. [Objective] T his study aimed to investigate the effects of H 2 O 2 and NO on flower development and AP 1 gene expression of off-season longan. [Method] N ine-year-old off-season Chuliang longan was sprayed with enhancers and blockers of H 2 O 2 and NO to analyze dynamic changes of flower development and AP1 expression. [Result] T he expression level of AP1 gene in off-season longan was improved during flower development. SNP and MV treatments up-regulated the expression level of AP1 gene in leaves and Especially, SNP treatment exhibited the most remarkable effect. DMTU treatment significantly inhibited the expression of AP1 gene in leaves and terminal buds during lateral primordium formation. L-NNA treatment slightly inhibited the expression of AP1 gene in leaves and exerted no significant effect on expression of AP1 gene in terminal buds. [Conclusion] It can be speculated that the enhancement of NO and H_2O_2 signals is conducive to flower development of off-season longan, while blocking H_2O_2 signals may inhibit flower development of off-season longan.