Abstract: The effect of different plant growth regulators on the quality of four- year- old‘Summer Black’grapes under protected culture was studied. It was indicated that 3 plant growth regulators could promote enlargement of grapes. The effects of CPPU and TDZ on enlargement of fruit weight, vertical and horizontal diameter were better than that of GA₃. Furthermore, soluble solids content dropped significantly when treated with 3 plant growth regulators. Soluble solids content treated with CPPU and TDZ was lower than that treated with GA₃. On the whole, it was appropriate to treat‘Summer Black’grapes two times with GA₃. It was recommended to apply 25 mg/L GA₃on full-bloom stage and 50 mg/L GA₃10 days later in production. Key words:‘Summer Black’grape; GA₃; CPPU; TDZ; fruit quality