Abstract: As a new type of filling material with excellent performance, calcium sulfate whisker has been widely used in many fields, such as plastics, papermaking and rubber. In this paper, calcium sulfate dihydrate (DH) was used as a raw material to synthesize calcium sulfate hemihydrate (HH) via hydrothermal synthesis followed by calcination, leading to anhydrous calcium sulfate (AH) whisker. The effects of calcination temperature and calcination time on the stabilization of calcium sulfate whiskers were systematically studied by SEM, TG, XRD and other analytical methods. The experimental results showed that the calcination temperature and the calcination time could effectively promote the stabilization of calcium sulfate whiskers at the temperature range between 200 °C and 600 °C. When the calcination temperature was 650 °C and the calcination time was 1 h, the obtained products were all dead roasted calcium sulfate (DAH). The crystal surface of HH showed hexagon channels, which contain the water crystals. Upon the treatment of calcination, the water molecules were evacuated out from the crystal along the channels, and the SAH with hexagon hollow holes were generated. Upon increasing the calcination temperature, the hollow channels of SAH collapsed due to the thermal motion of atoms in the crystals; and increasing the calcination time, the atoms continue to move and reorganize. On this basis, the DAH with stable structure was generated by controlling the calcination temperature and calcination time at appropriate values. Due to the dense structure of the DAH whisker, the access of water molecules into the crystal interior is dramatically limited. As a result, DAH is difficult to be hydrated, which endows the stabilization of calcium sulfate whisker. These results provide some fundamental basics for the selection of preparation technology parameters and the industrial production of the stabilized calcium sulfate whisker.