Abstract: For extending the life of purging plug, its thermo-mechanical stress fields were simulated to determine the reasonable specification of the slits.Firstly, based on the working properties of the purging plug and the purpose of research, its two-dimension plane strain finite element models were built by simplifying the structure and the boundary conditions of it.Then holding the line of the purging plug's specification and the form of the slits' distribution, the influence of the slits' sizes and numbers to the thermo-mechanical stress distribution of purging plug was studied.The results show that the areas of higher thermal stress of purging plug locate in the ends of the slits, and the areas that the stress changes drastically are around the slits too.Shortening the length of the slits can reduce the whole thermal stress that the purging plug suffered;prolonging the width of the slits definitely can reduce the stress on its ends too.Increasing the slits' number can also reduce its ends' stress, but it can increase the stress of the other areas either.