A method is introduced to directly measure the temporal structure of femtosecond XUV which has a narrow bandwidth using sub_picosecond duration laser. Calculati on shows that such a temporal structure can be reconstructed from the differenti al photoelectron energy spectrum excited by XUV or x ray, modulated by a laser field and measured at 90° or 0° with respect to the linear laser polarizatio n. The effectiveness and nonlinearity of the method are investigated. Energy res olution and bin(s) are important parameters for measurement and calculation. The method has a broad temporal measurement range and can be used for researches of dynamic processes associated with atomic motions.