Abstract: The objective of this experiment was to improve the photosynthetic efficiency and peach fruit quality in greenhouse. The photosynthesis, chloroplast activities and fruit quality were investigated by spraying 20 and 40 mg/L DA-6 (N, N-diethylaminoethyl hexanote). The results showed that 20 mg/L DA-6 significantly improved the net photosynthesis rate, stomatal conductance and chlorophyll contents. Hill reaction activities, non-cycle photophosphorylation activities, Rubisco and ATPase activities were increased when the peach tree was sprayed with 20 mg/L DA-6, compared with the control without foliar spray of DA-6. On the contrary, 40 mg/L DA-6 slightly decreased them. The results also indicated that 20 and 40 mg/L DA-6 both improved the fruit quality. 20 mg/L DA-6 significantly increased the fruit mass and soluble solid content, significantly decreased the content of titratable acid, and improved fruit quality. From the above results, it is concluded that foliar spray of suitable concentration of DA-6 can improve photosynthetic efficiency and fruit quality of peach tree in greenhouse.