The thermal behavior of aerostatic spindles is significantly affected by the multi-physics coupling phenomenon between the air film, the solid structure, and the temperature field of the spindle system. In this study, a novel simulation modeling method is proposed to investigate the multi-physics coupling phenomenon of the aerostatic spindle system, by which the elastic deformation and the thermal deformation of solid parts can be considered simultaneously to predict the thermal behavior of the aerostatic spindle. Besides, the variation in the performance of air bearing and the gravitational eccentricity of the shaft during the temperature rise process are also obtained, which provides an insight into the multi-physics coupling phenomenon of the aerostatic spindle. Finally, the temperature raise process of the aerostatic spindle system is measured to validate the proposed model.