A sintering method for a wick structure of a heat pipe includes the steps of inserting a shaft inside the pipe body such that a tapered head is assembled to the shrunk end to achieve a second positioning point, wherein another end of the shaft extending to the filling tool forms a first positioning point corresponding to the clamping section. The filling tool fills a wick structure into a uniform gap defined by the shaft and the pipe body and clamped by the first positioning point and the second positioning point. The wick structure is sintered and cooled to complete a heat pipe having wick structure of uniform thickness.