Based on a comprehensive survey of endogenous hormone in floral bud and characteristics of early defoliation during returning bloom,we indicated that:(1)The IAA and GA₃ in floral bud decreased after fruit harvest,while ABA showed up-down-up “S” curve.(2)Returning bloom of floral bud was controlled by the dynamic balance of the hormone.The rates of IAA/ABA,GA₃/ABA and (IAA+GA₃)/ABA showed up-down-up “S” curve after fruit harvest.The floral bud returned bloom,when IAA/ABA,GA₃/ABA and(IAA+GA₃)/ABA rate increased,while floral bud went into dormancy when the rate decreased.(3)The analysis of coefficients showed that the related coefficients for IAA/ABA rate and early defoliation rate,returning bloom rate in cv.Hosui were 0.805 and 0.774,respectively at the 5% significant level.The decreased of ABA in floral bud due to the early defoliation of ‘Hosui’ made the rate of endogenous hormone changes,which prevented the onset of dormancy of deciduous fruit trees with dormant nature and promoted the next growth cycle to commence,so the floral bud returned flower.