Abstract: To study the effects of spraying gibberellin on tillers and lodging of sweet sorghum.Cultivar sweet sorghum Jintianza3 was used as material, spraying gibberellin solvent of 50mg/L、100 mg/L、150 mg/l、200 mg/l、250 mg/l、300 mg/l、400 mg/l、500 mg/l、750 mg/l、1000 mg/l at 5 periods of 2-6 leaf stage respectively and the water was used as negative control.Results showed that the average tiller number of sweet sorghum was effectively decrease after spraying gibberellin, and reached the lowest level at 6 leaf stage in different treatment periods. The minimum tiller number lowered by 32.2%、30.6%、25.8%、43.5%、89.5% respectively comparing with the control at five periods，and the optimum concentration of gibberellin solvent was between 250-300 mg/L. Correlation analysis revealed that tiller number at seedling stage was significantly positive correlation with lodging rate, and was very significant positive correlation with the yield. The yield significantly increased after spraying gibberellin, and increasing effect of yield was weaker with the effect of controlling tillers, but it couldn’t cause yield reduction. Therefore, the optimum effects on controlling tillers was showed at 6 leaf stage with concentration of 250-300 mg/l, that could increase lodging resistance and keep the yield stable.