The study aimed to investigate the economic rate of potassium and molybdenum application for sugar beet (Beta vulgaris L.) in the Egyptian calcareous soil. The field experiment was conducted as complete randomized design using 36 plots each is one m2. Potassium showed a significant effect on the growth of sugar beet plant where increased the yield of the whole plant, root, shoot and sugar yield. Amino nitrogen was affected significantly by potassium fertilization, while the dry matter yield and sucrose percentage did show significant effect. The economical addition of potassium was 100 mg K/kg soil which increased the sugar yield by 24% and 35% for the first and second seasons, respectively. Addition of molybdenum as a micro-nutrient showed that the rate of 0.2 mg/kg soil was enough to cause the required effect where, the tubers yield were increased by 27% and consequently the sugar yield increased by 23%. There were no interaction between potassium and molybdenum in their effect on sugar beet growth and yield.