Evaporative crystallization of nano-particles involves a complicated multiphase mass and heat transfer process that is dependent on the crystal size in a temperature field. It becomes more complicated for the crystallization of ZnSe powders using this method because of multiprocesses including sublimation, crystallization, and decomposition. This work reports our preliminary studies on the evaporation process to two different sizes of ZnSe powders. We investigated the influences of crystal size on mass depleted between 200 and 800 °C. On the basis of our experimental data, a model of mass depleted of ZnSe nano- and micro-powder was proposed.