BACKGROUND: Suitable and useful usage of different kind of fertilizers is the main way for reformation and potential of soil fertility and increasing of crops yield. OBJECTIVES: This study was conducted with the aim of evaluating the effect of drought stress and potassium sulfate application on the crop production and qualitative traits of mung bean genotypes. METHODS: Current research was done according a factorial split plot based on randomized complete block design with three replications at two years in the summer of 2010 and 2011 at the Safiabad Agricultural Research Center, Dezful. Different irrigation levels (irrigation after 120, 180 and 240 mm of evaporation) belonged to main plot and potassium fertilizer (without fertilizer consumption, 37.5 and 75 kg.ha-1 from potassium sulfate source) with genotype (included the varieties of Parto, Indian mass and the promising lines VC6173, KPS1, Cn95) were placed in subplots. RESULT: The results showed that water deficit stress significantly affected the yield traits, stomatal conductance, harvest index and the amount of chlorophyll, so that severe and mild drought stress reduced the seed yield by 30.4 and 21.9%, respectively, compared to the optimal conditions. Among genotypes, the highest seed yield belonged to Pratto variety and VC6173 line were selected under optimal irrigation conditions and lowest one was related to KPS1 line. The use of potassium fertilizer increased the tolerance of all genotypes to drought stress. The use of potassium sulfate is due to its positive effect on the better absorption of other elements, especially nitrogen and phosphorus and increased tolerance to drought stress was effective. In general, drought stress had a significant negative effect on physiological traits of mung bean, and these characteristics also had a significant effect on the components of seed yield, so, potassium consumption had a positive and significant effect on physiological characteristics of the plant and Improved yield components. CONCLUSION: Optimal irrigation, potassium consumption of 37.5 kg.ha-1 and use of Pratu variety, Indian mass and promising VC6173 line were recommended. تفاصيل المقالة