Abstract: The paper aims to study the effect of 0.0075% brassinolideWA on growth and quality of pakchoi. A series of concentrations of 0.0075% brassinolideWA were sprayed at pakchoi seedling and growth stages. The result showed that the features of growth such as plant height, leaf width and quantity and plant biomass significantly increased after using different concentration of 0.0075% brassinolideWA. Compared with the control, the reproduction increased about 8.42%- 17.41% . The quality of pakchoi such as the content of vitamin C, soluble sugar and soluble protein also significantly increased whereas the content of crude fiber significantly reduced after using different concentrations of 0.0075% brassinolideWA. The content of crude fiber reduced from 1.12% of the control to 0.83%. The physiological indicators of pakchoi reached the better level and had no difference from the best when using 0.075 mg/kg of 0.0075% brassinolideWA. Therefore, the concentrations of 0.050-0.075 mg/kg were recommended to use in the field.