Abstract: In order to clarify the influence mechanism of boron on sugar beet leaf, provide theoretical basis for boron application in practice and production, the experiment was conducted under water culture condition to study the effect on boron level、leaf structure and properties of suagr beet under different boron treatments. Sugar beet seed HI0099 was selected as experimental material. Four nutrition concentrations of boron were set: 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).The results showed that: boron content increased as boron level improving. In boron stress condition, the chlorophyll content、net photosynthetic rate and leaf transpiration rate were all decreased. whereas intercellular CO2 concentration first decreased and then increased in boron deficient condition, in boron toxic condition it remains rising level. Boron stress increased the thickness of leaf、palisade parenchyma and spongy parenchyma. However, boron toxicity decreased the thickness of upper and lower epidermis. The results showed that boron stress changed the boron level and leaf structure, decreased leaf property in some degree. Thus, applying boron fertilizer reasonably to improve leaf structure and photosynthetic characteristics has important practical significance in sugar beet production.