Abstract: The discharge of the liquid on the orbit will produce more and more millimeter space debris as accompanied with the frequent space activities. Due to the heat dissipation uncertainty during the sublimating process, their long-term presence on the orbit will endanger the space environment. Taking water as an example, the paper analyzes numerically the sublimating process of the liquid particle in the solid state on the orbit. The results show that the solar absorptivity of particles plays most important roles in the sublimation. Furthermore, the increase of the solar absorptivity and the decrease of the single particle’s average mass will improve the heat transfer during the sublimating process.