The present study was carried out during 2017-2018/2018-2019 on 5 years old plum trees cv. (African Rose) budded on Mariana rootstock to disscus the importance of thinning flowers and fruits on plum fruit quality. Treatments were as follows: control trees without thinning, hand blossom thinning, hand fruit thinning, Ethephon at 100 ppm, NAA (Naphthalene acetic acid) at 20 ppm and BA (6-Benzyladenine) at 400 ppm. Results indicated that, all thinning treatments increased fruit drop and the highest fruit drop % was found with Ethephon treatment at 100 ppm in both seasons. Also, all treatments reduced fruit number per tree compared to control but increased fruit yield (4-6 kg/tree) and that may be as a result of increase fruit weight and size which subsequently increase yield price. Thinning treatments under study increased fruit physical characteristics and the highest fruit weight was obtained from hand fruit thinning treatment in both seasons. All thinning treatments advanced harvest date and increased yield. Data also revealed that the highest percentage of carbohydrates and C/N ratio in leaves were recorded with hand fruit thinning treatment compared to the other thinning treatments. So, we can recommend this treatment to early harvest date, high fruit yield and fruit quality, subsequently higher fruit yield price.