Screening of crop genotypes with high K efficiency plays a fundamental role in understanding their physiological mechanisms. In this study, pot culture experiment was conducted to reveal the differences in uptake and use of K among 56 barley varieties. The coefficient of variation (CV) of K uptake (Ku) and K dry matter production index (KDMPI) of these varieties were higher than other indices and both Ku and KDMPI were significantly different among the barley varieties. Furthermore, Ku and KDMPI were positively correlated with dry matter weight (DMW) during the whole growth period; K use efficiency (KUE) and K harvesting index (KHI) were significantly related to dry grain weight (DGW) at maturing stage. Through cluster of these indices, Sandrime and AC Westech were found to be the most K-efficient and K-inefficient genotypes of barley, respectively. Significant differences were observed in uptake and use capacity of K between the two genotypes. During the whole growth period, Ku, K dry matter production efficiency (KDMPE), KDMPI and DMW of the K-efficient genotype were found to be 1.5-1.8, 1.4-2.3, 2.1-3.9, and 1.7-2.1 times higher than those of the K-inefficient genotype, respectively, and at maturing stage, DWG, KUE, and KHI of efficient genotype were higher than those of the inefficient one. The results also showed that Sandrime was the most efficient candidate among the tested varieties for K efficiency and further studies should be conducted to investigate its physiological and biochemical characteristics. Screening of crop genotypes with high K efficiency plays a fundamental role in understanding their physiological mechanisms. In this study, pot culture experiment was conducted to reveal the differences in uptake and use of K among 56 barley varieties. The coefficient of variation (CV) of K and K DMPI were positively different with the dry matter weight (DMW) During the whole growth period; K use efficiency (KUE) and K harvesting index (KHI) were significantly related to dry grain weight (DGW) at maturing stage. Through cluster of these indices, Sandrime and AC Westech were found to be the most K -efficient and K-inefficient genotypes of barley, respectively. Significant differences were observed in uptake and use capacity of K between the two genotypes. During the whole growth period, Ku, K dry matter production efficiency (KDMPE), KDMPI and DMW of the K-efficient genotype were found to be 1.5-1.8, 1.4-2.3, 2.1-3.9, and 1.7-2.1 times higher than those of the K-inefficient genotype, respectively, and at maturing stage, DWG, KUE, and KHI of efficient genotype were higher than those of the inefficient one. The results also showed that Sandrime was the most efficient candidate among the tested varieties for K efficiency and further studies should be conducted to investigate its physiological and biochemical characteristics.