Abstract: Taking Hongjiang orange adult trees as materials, this paper studied the dynamics of fruit retention rate and sugar, acid contents during on -tree storage. One month before the pericarp full coloring, 5 treatments were set, including foliar spray GA3+ applying soil nitrogen fertilizer + mulching plastic film, foliar spray GA3+ applying soil nitrogen fertilizer, foliar spray GA3+ mulching plastic film, applying soil nitrogen fertilizer and mulching plastic film. The results showed that, all the treatments had good effects on on-tree storage. The contents of sugars including fructose,glucose and sucrose in flesh fruits of all the treatments changed by single-peak curve, and all the peaks appeared on the 42th day after treatment. The contents of total acid in flesh fruits of all the treatments dropped quickly in the 42 days after treatment, and dropped to the bottom on the 42th day, then all the contents changed gradually. During the period from the late December to the middle January of the next year, the content of soluble sugar in flesh fruits was higher, and the ratio of sugar/acid got better too, so it was proposed to harvest during this period.