Abstract: To provide the physiological basis for apple in middle Guizhou Province, the photosynthetic characteristics, main factors impacting photosynthetic rate（Pn），as well as their effects on fruit yield and quality were elucidated in the present work. The results showed that‘Red Fuji’（14.87 μmol · m-2 · s-1） demonstrated a superior photosynthetic ability to‘Royal Gala’（13.57 μmol · m-2 · s-1）. They exhibited diurnal fluctuations of Pn with two peaks in the summer, and an obvious midday depression was observed in both cultivars, which was primarily ascribed to the excessive photosynthetically active radiation（PAR）and reduced stomatal conductance（Gs）. Photosynthesis was most predominantly affected by PAR, followed by the leaf temperature（Tl），and were slightly influenced by relative humidity（RH） and air CO2（Ca）. The yields of two cultivars were highly correlated to PAR and Pn. The quality parameters，including fruit weight，soluble sugar content, and sugar acid ratio，were positively correlated with PAR and Pn，with the exception of vitamin C content. Based on the photosynthetic features, some technical measures on apple cultivation in the middle of Guizhou were put forward to promote light use efficiency.

Key words: apple, Guizhou, photosynthesis, yield, fruit quality