An elastic-plastic shakedown solution is established for the shadedown analysis of the structure under moving loads.On the basis of the Melan’s static shakedown theorem，this method is developed by searching for the best residual stress field，and calculating the actual elastic stress field subjected to the moving loads.This method avoids the operation of mathematical programming in traditional method of shakedown analysis，and therefore obstruction due to large scale mathematical programming is overcome. The validity of this method is verified by comparing the results of the previous study. Based on this method，the upper bound type 1 shakedown limit kI and static shakedown limit kSD of railway subgrade are presented. A sensitive analysis is also presented, showing that the shakedown limit remains stable if the distance between the loads L and rails B is longer than 10a，so that the upper bound type 1 shakedown limit kI is shown. Meanwhile, by means of investigation on the influence of Poisson′s ratio and internal friction angle, it is found that the static shakedown limit kSD diminish marginally with the increase of Poisson′s ratio, while both the upper bound type 1 shakedown limit kI and static shakedown limit kSD experience a steadily growth with the increase of internal friction angle. A design method for subgrade is finally proposed based on the envelope diagram of shakedown limits, which can provide guidelines for design and safety assessment of railway subgrade.