Abstract: The study is to investigate the effects of boron application on morphological parameter and physiological activity of sugar beet root, elucidate the influence mechanism of boron application on root properties and provide a theoretical basis for boron application in sugar beet production. Sugar beet cultivar ‘HI0099’ was used as an experimental material, four boron concentrations were designed: very deficiency (T₁, 0.05 mg/L), deficiency (T₂, 0.5 mg/L), normal (T₃, 2.0 mg/L), excessive toxicity (T₄, 30.0 mg/L). Root dry weight, shoot-root ratio, root morphology and activity were determined to analyze the growth and physiological laws of sugar beet. The results showed that: boron deficiency and toxicity both decreased dry weight of sugar beet root, boron deficiency decreased shoot-root ratio, boron toxicity increased shoot-root ratio. In boron deficiency and toxicity condition, root volume, root diameter and root activity all exhibited a downward trend, and the reduction amplitude increased as the developmental process went on. Comprehensively considering the results, boron stress decreased root activity, influenced the growth and dry matter accumulation of root, then caused the deterioration of root property and the maladjustment of shoot-root ratio. Thus, the reasonable boron application can improve root growth and physiological activities and regulate shoot-root ratio, and has practical meaning for the high quality and high yield cultivation of sugar beet.