Taking pantograph frame as the research object, a load spectrum Compiling method suitable for accelerated life test of pantograph frame is proposed. Firstly, the coupling dynamic model of the pantograph was established based on the finite element method, and the load spectrum of the upper frame was obtained by multi-body dynamics simulation. The dynamic stress analysis method is used to convert the time-history data of the upper frame load into the stress spectrum of the weld concerned. At the same time, the statistical characteristics of the stress spectrum amplitude method are studied, the results show that the amplitude obeys Weibull distribution, and the eight-order one-dimensional loading spectrum is established by extrapolation of the parameter method. In order to facilitate the loading of the test bench actuators, a load back push method is put forward, and the error of the contrast acceleration spectrum is controlled within 6% through the test bench data. This method can provide reference for fatigue life test and life prediction of pantograph components.