Drought is a major environmental stress affecting agricultural productivity around the world. Application of potassium to plants can increase the ability of plants to tolerate drought stress while maintaining turgor pressure at low leaf water potentials. In this research, the effect of potassium applications under drought stress on some physiological parameters of sugar beet, which is a strategic plant, was investigated. In the experiment, irrigation levels were kept at 33%, 66% and 100% of field capacity. Different doses (10-20-40-80 mg kg(-1)) of potassium were applied to the plants. The plants were grown with Hoagland nutrient solution in the growth chamber. Relative water content increased at the 33% irrigation level with potassium applications to 67.39, 68.93, 68.20 and 74.41%, respectively, while membrane damage and MDA content decreased (70.66, 71.10, 65.91, 68.43% and 35.94, 25.38, 21.74, 18.84 nmol g(-1)). In addition, vitamin C and SH compounds decreased at the 33% irrigation level with potassium applications to 252.15, 198.40, 125.06, 134.25 mu g g(-1)and 69.16, 66.94, 55.89, 54.59 mu g g(-1), respectively. According to the results obtained from the experiment, the potassium applied to the plants under drought stress led to an increase in the relative water content and the reduction of membrane damage, and especially to the reduction of non-enzymatic antioxidants produced for defence purposes when faced with plant stress. Therefore, it can be said that potassium may play a critical role in reducing the negative effect of drought stress in sugar beet.