Abstract: A comprehensive plot experiment of chemical regulation was carried out during the differentiation of flower buds in November-December and physiological fruit drop in May June,1992-1994 Combination of 6-BA 200 mg/L+B9 2000 mg/L and GA3.10 mg/L+2,4-D 5 mg/L were used respectively.The results showed that the increasing amount and rate of the treated winter shoots was only 35.03% and 37.59% that of the control.The flushing rate of the flower clusters was up to 92.33%, increased 81.75% over that of the control,markedly promoting the flower bud differentiation.The rate of degradation in inflorescene decreased,only 15.28% that of the control.The branch clusters of flowers increased by 30.02%.The treatments increased 67.40% in fertile fruits and 48.00% in fruit clusters.The average yield per tree was up to 57.00 kg,an increase of 61.61% over that of the control.The flushing rate of the flower clusters was up to 90.41% with an average 46.10 fertile fruits per cluster.The total yield of 604 treated trees(2.37 hm2)was up to 38744.70 kg with average yield of 64.20 kg/tree, reaching a higher level in present longan production.