Abstract: The effects of different potassium (K⁺ ) concentration on seedling growth, physiological and biochemical indexes of sugar beet were studied using half-strength Hoagland nutrient solution. The results showed that the dry weight of leaves, petioles, roots and of the whole plant of sugar beet seedlings increased with the increase of K⁺ concentration, and arrived the highest when K⁺ concentration was 3.00 mmol/L. Besides, K⁺ level in roots, petioles and leaves, accumulation amounts of total nitrogen (N), phosphorus (P) and potassium (K) in seedlings, petioles and leaves water content, relative water level in leaves and leaf area increased gradually with increase in K⁺ concentration, however, these indexes showed no obvious difference between treatments of 3.00 and 6.00 mmol/L K⁺ . Nevertheless, the contents of chlorophyll a, chlorophyll b and chlorophyll a+b, activities of SOD and GPX, and N level in roots, petioles and leaves decreased gradually with the increase in K⁺ concentration, while no notable difference was observed when treated with 3.00 and 6.00 mmol/L K⁺. On the other hand, CAT activity, P content in roots, petioles, and leaves showed no significant change or changed with no rule. Under this experimental condition, we concluded that 3.00 mmol/L K⁺ was the optimum K⁺concentration for sugar beet seedling growing.