To make full use of the gelation activity of hemihydrate phosphogypsum and use hemihydrate phosphogypsum as mine filling cementing material, the physicochemical properties and micromorphology of hemihydrate phosphogypsum were analyzed by XRD, XRF, and SEM. Through the orthogonal experiment, the best ratio of hemihydrate phosphogypsum filling materials was obtained: the content of quicklime is 1.5%, the content of tailings is 0%, and the content of crystal water is 5%. The single-factor experiment shows that the strength of hemihydrate phosphogypsum has a positive correlation with the dosage of lime and the stirring time, and is negatively related to the content of crystal water, the content of water soluble phosphorus, and the amount of tailings mixed with hemihydrate phosphogypsum. To make the 3 d strength of the hemihydrate phosphogypsum filling material reach 3 MPa, the amount of lime in the filling material should no less than 1.5% and the stirring time no less than 10 minutes. At the same time, the content of water soluble phosphorus in the raw material of hemihydrate phosphogypsum should be less than 4%, the content of crystalline water should be less than 10.3%, and the content of the tailings no more than 60%. Microanalysis shows that the strength of hemihydrate phosphogypsum filling body is influenced by the crystal morphology of hydrated phosphogypsum, the strength of the contact, and the volume rate of hydration products.