Field experiments were carried out at the Experimental Farm of Arab ElAwammer Research Station, Agriculture Research Center, Assiut, Egypt, during the two successive growth seasons of 2014/2015 and 2015/2016, to study the effect of applied Bio-stimulants (control, potassium humate 9.6 kg/ha, yeast extract 5g/l and both of them) under three regimes of drip irrigation (100%, 80% and 60% of reference evapotranspiration ETo) on potato yield. Plant high (cm), number of branches, tubers weight/plant (g), marketable tubers weight /plant (g), small tubers weight / plant (g), tubers potato weight (ton/ha), marketable tubers (ton/ha), and irrigation water used efficiency (IWUE) were evaluated. The obtained results could be summarized as follows: Irrigation water used efficiency was significantly increased with applied potassium humate plus yeast extract under different drip irrigation regimes. The results indicated that no significant increases on tubers potato yield and its components when crops irrigated with 100 % of reference evapotranspiration (ETo) compared with 80% of ETo but increasing significantly compared irrigation with 60% of ETo. Application of potassium humate plus yeast extract increased the potato tubers weight with 34.9%, 21.3% and 35.6% compared control (without application) under three regimes of drip irrigation, respectively. The highest irrigation water used efficiency (10.8 kg/m3 ) in this study was resulted from the interaction between the irrigation with 80% of ETo and the application potassium humate plus yeast extract.