The invention provides a method for detecting the content of sulfotep in a chlorpyrifos mono-agent and a mixed agent and relates to the technical field of material content detection. According to the method, a capillary column with the wall coated with the non-polar stationary phase is adopted for sample component separation, a flame ionization detector is adopted, n-octadecane is taken as the internal standard substance, and gas chromatography quantitative determination is conducted with the peak area or peak height internal standard method. By creatively adopting the capillary column with the wall coated with the non-polar stationary phase for sample component separation, separation column efficiency is improved greatly; meanwhile, by creatively adopting n-octadecane as the internal standard substance, detection cost is low; more importantly, the content of sulfotep in the chlorpyrifos mono-agent and the mixed agent can be detected quite accurately, and the detection result is quite accurate and high in precision.