Abstract: Effect of GA3 on making berry seedless by the treatment of flowering period at different climate was researched. Only 3.5~4cm of infra-spike was remained and treated in every inflorescence. Berry flowering period was divided into 3 periods according to the characteristics of inflorescence blooming. It was defined as the earlier stage, the full stage, and the final stage of grape blooming when the end one third, the middle one third, and the front one third of spike flowered differently. The spike was dipped using 12.5 mg/L、25.0 mg/L、37.5 mg/L和50.0 mg/L of GA3 at different flowering period separately at different climate. The results were as follows: Every treatment increased the berry seedless percentage at different level. The soluble solid content increased 1~3 percent. The fruit mature period was advanced by 7days. The average fruiting rate was reduced by 20%. Based on the investigation, the researcher put forward that the concentration and treatment period of GA3 were different at different climate for advancing the seedless effect. The concentration of 25.0 mg/L and 37.5 mg/L of GA3 was suitable at the beginning of flowering when the precipitation was less and the temperature was higher, on the contrary, the treatment of 37.5 mg/L and 50.0 mg/L of GA3 was most right at the full flowering.