Abstract: The aim of this experiment was to study the fruit growth-development rule of flat nectarine and the formation and variation of the main quality indexes. With‘Ziyue’,‘Xinyue’and‘Meiyue’as the experimental materials, this paper studied the vertical and horizontal diameter of the fruit, the single fruit weight, the total soluble sugars, the titratable acid, the starch content and the fruit drop during fruit development of flat nectarine. The results showed that the fruit growth rules of‘Ziyue’,‘Xinyue’and ‘Meiyue’were basically in accord with the double“S”curve of the stone fruits. Along with the fruit development, for‘Xinyue’and‘Meiyue’, the content of total soluble sugar displayed a tendency of increase gradually, the titratable acid content increased at first and then exhibited a decline, and the starch content of the fruit had a descending trend. Based on the fruit drop wave observation,‘Meiyue’had three obvious premature drop peaks.‘Ziyue’and‘Xinyue’had two obvious premature drop peaks, respectively, both of them had a longer first drop period, and the reason was probably related to the fact that the fruit development periods of ‘Ziyue’ and ‘Xinyue’ were shorter than that of‘Meiyue’. Overall, the fruit development rules of flat nectarine and the variations of its quality-related factors were similar to that of the normal peach and nectarine.