Water stress is considered one of the most widespread limitations to crop productivity and yield stability causing yield reductions between 10 and 30 % of sugar beet. Drought tolerance is a complex trait controlled by many metabolic pathways and genes. Identifying a solution to increase the tolerance of plants to drought stress is one of the grand challenges in plant biology. This study provided compelling evidence of increased drought stress tolerance in four sugar beet cultivars namely Del 1135 R2, Collins, BTS 7245 R1 and Aseel planted under three levels of field capacity (100 -75 -50 % FC) and treated with foliar application of ascorbic acid at three concentrations (0-350-550 ppm). Study was established throughout two winter growing seasons 2021/2022 and 2022/2023 at the experimental farm of Agronomy Department-Faculty of Agriculture- Suez Canal University in Ismailia, Egypt. Results were observed that drought stress expressively reduced plant growth, photosynthetic pigments, and sugar yield, while foliar application of ascorbic acid caused significant increase on growth and yield parameters. It can trigger some physiological processes and stimulate total soluble sugars in plants. Tolerance indices like MP-TOL-YSI-GMP indicated that cultivars Aseel and Collins with treatment 550 ppm AsA gave the highest yield and gave the most tolerant treatments. Furthermore, values of genetic parameters; GVC, PVC, GA and h2 exhibited increasing in number of studied characters of root and shoot that can used for selection in successive breeding programs.