Abstract: An effective and convenient method for determination of dimethyl fumarate ( DMF) in pastry by pressurized capillary electro-chromatography (pCEC) with ultra-violet detection was developed. The samples were extracted with methanol. The separation was performed on a reversed phase C18column in an isocratic mode with 220nm as the UV detection wavelength. The effects of ratio of organic phase and separation voltage on separation efficiency were optimized. The mobile phase was composed of acetonitrile and water (3∶7, v/v) , at a pump flow rate of 0.05mL/min. Under the optimal conditions, the linear range of DMF was 2.0¹00mg/kg with correlation coefficient higher than 0.9998. The mean recoveries were 85.5%⁹3.6% and the relative standard deviations (RSD) were less than 5%.