Abstract: In order to study the effect of bio organic fertilizer on apples,the experiment used no bio organic fertilizer as the control（CK） and set four bio organic fertilizer dosages,namely 1 500 kg/hm~2（T₁）,2 000 kg/hm~2（T₂）,2 500 kg/hm~2（T₃）,and 3 000 kg/hm~2（T₄）.This paper studied the differences in photosynthetic characteristics,yield,and quality of apple leaves.The results showed that the application of bio organic fertilizer could significantly improve the net photosynthetic rate,stomatal conductance,and transpira‐tion rate of apple leaves.The yield of apple showed a gradually increasing trend with the increase of application amount,and there was no significant difference in photosynthetic characteristics between T₃and T₄treatments.Bioorganic fertilizer reduced the titrat‐able acid content of apple fruit,significantly increased soluble sugar,soluble solids,and flesh hardness.There was no significant dif‐ference in soluble sugar and flesh hardness between T₃and T₄treatments.Therefore,when the application amount of bio organic fer‐tilizer is 2 500 kg/hm~2,the improvement effect of apple photosynthetic capacity and yield is obvious,and the quality is good,which can be applied in apple production.