Abstract: 【OBJECTIVE】To provide relative evidence for the regulation of flat peach fruit quality and to determine the proper time for fruit picking, the changes of quality-related factors during fruit growth and development of flat peach (Prunus persica L. Batsch, cv. Yingger) were studied at present research.【METHOD】Flat peach fruits of "Yingger" were picked every 10 days during fruit growth and development. Vertical diameter, horizontal diameter, fresh weight, soluble solid content (SSC), titratable acidity (TA) and ascorbic acid were measured during storage.【RESULTS】The results showed that the whole fruit development period of Yingger flat peach was around 100 to 110 days after fully blossom. The changes of horizontal and vertical diameters showed the same trend with the change of fresh weight. Soluble solid content increased till 70 days after fully blossom and then decreased smoothly. Besides, ascorbic acid increased steadily till 50 days after fully blossom, and then decreased. After 90 days, ascorbic acid content increased a bit and stayed constant until picking, while the content of titratable acidity declined all the time. 【CONCLUSION】Thus, Yingger flat peach shows its own characteristics in Xinjiang and the best time for picking up the fruit is around 100 days after fully blossom.