Cucumber was cultured in open-top CO2 controlled chambers to study the interactive effects of elevated CO2 and potassium (K) on the growth of cucumber. The results indicated that either elevated CO2 or K supply enhanced the dry matter accumulation of cucumber, and the maximum was obtained at elevated CO2 and 200 or 300 mg/kg K supply. Across all K treatments, elevated CO2 reduced N, P, K, Na, Ca and Mg concentrations in cucumber. And all K treatments did not significantly affect N, P, Ca and Mg concentrations in cucumber, while K concentration in cucumber significantly increased with K supply increased. Cucumber had the highest mineral nutrient uptake at elevated CO2 and 200 and 300 mg/kg K supply. Therefore, in the future elevated CO2 environment, more K supply will stimulate the uptakes of N, P, K, Ca and Mg and the growth and high productivity of plant.