This study was conducted to explore the effects of drought stress and different levels of potassium sulfate on yield and yield attributes of grain sorghum at Agriculture and Natural Resources Research Station of Sistan during year of 2009. Treatments were arranged in a split-plot lay out based on a randomized complete block design with three levels of drought stress as main plot (irrigation at 70%, 50%, and 30% field capacity) and five levels of potassium sulfate as sub plot (0, 100, 150, 200 and 250 kg ha-1) in three replications. Drought stress by reducing the yield components, especially the number of panicle per plant and one-hundred grain weight reduced grain yield. Maximum yield (3499 kg ha-1) and biological yield (14464 kg ha-1) was obtained at 70% FC. Grain and biological yields for the plants irrigated at 70% FC were 58.5% and 27.4% greater, respectively, than the yields of the plants irrigated at 30% FC. Potassium sulfate at the highest rate increased grain and biological yield by 28% and 22%, compared to control respectively, Through improving growth conditions. Interaction effect between drought stress and potassium sulfate on all studied traits was significant and optimum soil K levels protect plants from drought. These observations indicate that adequate K nutrition can improve drought resistance of sorghum.