By taking thermal baking process of foaming gypsum mold as a research object, the temperature variation, dimensional changing, and organizational transformation of the foaming gypsum mold in the overall thermal baking process were studied using K-type thermocouple, multi-channel temperature logger, vernier caliper, and Scanning Electron Microscopy (SEM), respectively. The results indicate that the temperatures of the internal points lag behind the process temperature entirely; the temperature difference curve of internal point gradually rises with the increase of heating temperature and the time for keeping warm. By the slough off of the internal free crystal water and the corresponding crystal transformation of gypsum, one-dimensional size in the length direction of mold first continuously declines and then increases slightly, the shape of gypsum grain changes from acicular shape to bulky cylindrical or lamellar appearance, subsequently transformating to needle morphology shape.