When heating and calcining the dehydrate gypsum and chemical gypsum (ardealite, desulphurization plaster, fluorgypsum), the dehydrate gypsum was decomposed, we get the semi-hydrated gypsum, ie.plaster of Paris. According to the temperature and pressure during decomposition, the products include high intensity gypsum and plaster of Paris. They are the same in the process of mechanization manufacture the plaster of Paris. The plaster breaking system, calcined system and grinding aging system are the main parts. The roller breaking machine and so on can be used as the breaking equipment. The continued and discontinued revolving kiln, continued and discontinued vertical pot, heat-conductive oil boiler or drying machine can be used as the cacined equipment. The calcined process: one is grinding after fired, the other is fired after grinding. We can choose Romans mill, vertical mill, peters mill as the grinding equipment. The whole process is as following: Gypsum ----- homogenization ---- rough breaking --- detailed breaking ----Measurement (calculating) ----calcined (oil coal, dust-collector)---- homogenization(dust-collector)----grinding(dust-collector)---aging (dust-collector)----- packing