In recent years, thulium-doped fluorozirconate (ZBLANP) glass has become one of the promising materials in the field of the laser cooling of solids. However, up to date, the theoretical studies on the laser cooling of the Tm3+:ZBLANP fiber and their experimental results have not been reported. In this paper, we have developed a simple theoretical model to discuss some basic problems in the laser cooling of solids. The influences of the fluorescent quantum efficiency, the pump power, the change of fluorescence wavelength and the black-body radiation on the laser cooling effect for the Tm3+:ZBLANP fiber are discussed in some detail, and some interesting and important results are obtained. These results will provide the reliable theoretical basis for further experimental study on the laser cooling of the Tm3+:ZBLANP fiber.