Abstract: The aim is to provide theoretical basis for the rational application of potassium and sodium in sugar beet production. Using sugar beet variety ''ST13092'' as material, three K+ levels (0.03, 1.5 and 3 mmol/L) and three Na+ levels (0, 1.5 and 3 mmol/L) were set under hydroponic conditions. At the same time, K+ and Na+ interacted for a total of 9 treatments. After 3 weeks of culture, the effects of different potassium and sodium levels on water potential, relative water content, chlorophyll content, photosynthetic characteristics, Na+ and K+ content, N, P and organic acid content of sugar beet seedlings were determined. The dry weight, leaf area, water potential, relative water content, transpiration rate, stomatal conductance, net photosynthetic rate and intercellular CO2 concentration of sugar beet seedlings increased significantly with the increase of K+ supply level and Na+ supply level, while the contents of chlorophyll a, chlorophyll b, N, P and organic acids decreased. When both K+ and Na+ were 3 mmol/L, the water potential, relative water content, transpiration rate, stomatal conductance, net photosynthetic rate, intercellular CO2 concentration, Na+ and K+ contents reached the maximum, and chlorophyll a and chlorophyll b contents, N, P contents reached the minimum.Potassium, sodium and their interactions not only directly increase the water potential and leaf area of leaves, promote photosynthesis, but also increase the osmotic regulation of potassium and sodium ions, reduce the role of organic osmotic regulation, and indirectly improve the utilization rate of photosynthetic products, promote the growth of seedlings, and regulate the content of N and P in plants.