A field research was conducted at the garden of fruit institute of Maoming City,Guangdong Province in 2000 and 2001, in order to study the effects of chemical regulators,which mainly contain the potassium chiorate(KClO₃),used in different seasons on flowering and fruit quality of longan(Dimocxarpous Longanna).The experiments indicted that the effect of inducing flowering(%) were significantly difference in different seasons.The effect of inducing flowering(%)of the chemical regulators in dried season were better than that in wetness season.The off-season longan fruit quality is different from the usual harvest fruit.An improvement in fruit quality was observed in fruit harvesting in later spring and early summer.Bigger fruit weight,higher ration of eatable part, less weight of seeds pit and lower acid degree were observed in later spring and early summer longan fruit.It suggest that using the chemical regulators in early autumn and harvesting fruit in later spring or early summer be suited to the off-season longan fruit production in the research region.