Abstract: Phosphogypsum is one of the important raw materials for the preparation of anhydrous gypsum and hemihydrate gypsum. Compared with anhydrite, hemihydrate gypsum as a polymer filling material has a simple preparation process and low energy consumption. This study prepared hemihydrate gypsum/polymer composites by melt blending with polymer as matrix and hemihydrate gypsum as filler. The composite's mechanical properties, thermal properties, oxidation properties, corrosion properties, and microstructure were tested. The results show that hemihydrate gypsum is compatible with the polymer and can reach hyper dispersion at a high dosage. When the mass loss temperature of the hemihydrate gypsum composite is 5%, the temperature is 350℃. After soaking in strong acid, strong alkali and concentrated salt, the mass losses of hemihydrate gypsum Polypropylene (PP) composite materials were 0.024%, 0.03% and 0.015% respectively. It indicates that the composite material has good corrosion resistance. Compared with pure Polyethylene (PE), the tensile properties of PE composites with a hemihydrate gypsum content of 20% have increased by 26%, and the oxygen index of PE composites with a hemihydrate gypsum content of 70% has increased by 8.6%. The melt flow rate of the composite material is 10-40 g/10min. The heat distortion temperatures of the hemihydrate gypsum PE composite material and the hemihydrate gypsum PP composite material are approximately 90℃ and 150℃ respectively. The above data indicate that this composite material has excellent processing performance, and the hemihydrate gypsum composite material also has good durability and heat resistance. The application of hemihydrate gypsum PE composite material in DN400 pipes was preliminarily studied, with a ring stiffness of 8.2 kN/m², indicating that hemihydrate gypsum PE composite material has a very good application prospect in the double-arm corrugated drainage pipes of buildings