The deterioration in area of plum orchards, in addition to the lack of productivity, resulted in an insufficient yield of plum. Some stimulants were investigated in this study during 2016 and 2017 seasons to improve fruit set; yield and fruit quality of Hollywood and Pioneer plum cultivars. Trees were treated with sprayed by with 1.0 and 1.5 ml/l of Daiblon k10 (contains 10% w∕w free amino acids and 10% w∕w potassium) or 4.0 and 6.0 ml/l of Essential Egy (contains mineral nutrients; natural Organic substance and 4.5 % L-amino acids). Other trees were treated with Humic acid as Actosol® (6.0 % w ∕ v potash and 20 % w ∕v Humate) at 5.0 ml/l /tree as spray foliar treatment or 30 ml/l /tree as soil application beside (control). The treatments were done at three times (at 30 % of flowering; 70% flowering and at full bloom) in each season. All trees were grown in sandy soil at El- Nubaria region, Behera Governorate, Egypt. A complete randomized block design was used with three replicates and each one was represented by one tree. During this investigation fruit set (%); yield (kg/tree); some physical and chemical fruit properties, as well as some mineral contents of leaves, were determined. Results cleared that the highest of both fruit number and yield (Kg∕ tree) were obtained when trees of Hollywood were sprayed with Essential Egy at 4.0 ml/l while the highest values of fruit set% and SSC were gained when trees were sprayed with 6.0 ml/l of Essential Egy. Spraying trees with Humic acid caused the highest leaf N and K content. All treatments under study gave variable effects on of total chlorophyll content. With regard to Pioneer cultivar, results showed that Essential Egy at 6.0 ml/l significantly increased fruit set %; fruit number per tree, yield (kg/tree and P content compared with Essential Egy at 0.4 ml/l which significantly increased SSC. Humic acid soil application significantly increased leaf N and P content. Spraying trees with Humic acid recorded the highest significant N and K content. Daiblon K10 at 1.0 ml/l gave the maximum total chlorophyll content. Thus, it can be recommended that spraying Hollywood and Pioneer cultivars with Essential Egy at 4.0 ml/l or 6.0 ml/l at three times (30 % of flowering; 70 % of flowering and at the full bloom) will increase plum yield and improve fruit quality