AbstractAttempts had been made to provide evidences insight into the pattern and physiological mechanism of sweet cherry fruit dropping. However, the fruit abscission pattern and mechanism underlying the heavy fruit dropping in insufficient chilling regions, especially the roles of interior factors including carbohydrates and hormones in abnormal fruit dropping, has not yet been better understood so far. Currently, four five-year-old sweet cherry (Prunus avium L.) cultivars, i.e., ‘Santina’, ‘Brooks’, ‘Sparkerry’ and ‘Black Pearl’, which were grown in Weining County (104.28° E, 26.86° N), Guizhou province of China, were used as materials to elucidate the physiological fruit abscission pattern of sweet cherry and the chief interior causes for the heavy fruit dropping in insufficient chilling region of China. It was explicated that the abscission pattern of sweet cherry fruit somewhat varied among the cultivars in a low chilling region. Higher rate of pollen germination and longer polar axis length was proved to be remarkably beneficial to fruit development. A comparative anatomic dissection of fruit stalk between the retention and dropped fruit elaborated that there is obvious difference in the microstructure with the progress of fruit development. The discrepancy was mostly showed by the cell space of abscission zone tissues for the dropped fruit enlarged gradually and was remarkably larger than that of the retention ones. Furthermore, the imbalance of endogenous hormones in fruit is a crucial trigger for fruit dropping with the progress of fruit development, particularly the active ZR, GA, as well as IAA levels in fruit are positively correlated to fruit setting, conversely, ABA played a negative role in fruit retention. Moreover, carbohydrate contents in retention fruit were considerably higher than that of the dropped ones during the fruit development, however, the contents of glucose and fructose in dropped fruit did not reach the required threshold which was possibly a vital cause leading to fruit abscission.