Abstract: In view of the environmental pollution problems caused by the piling up of phosphogypsum and the problems of high filling cost, large amount of cement or other solid materials, and the filling body is unable to contact the top, therefore, a new type of complex phase condensate expansion was prepared. The filling material was optimized by orthogonal test range analysis, variance analysis, multivariate nonlinear regression analysis and data visualization, its formation mechanism was also studied by means of microscopic analysis such as XRD and SEM and so on. The filling composite material is mainly composed of four kinds of materials, namely hemihydrate phosphogypsum (HPG), amorphous phase condensate (SAP), gas phase introduction agent (GPA) and surface hydrophobicity (HA). The filling body is three-phase with solid, liquid and gas. The prominent feature is solidifying under the condition of non-solid volume rate of 87.6%, the compressive strength of 3 days can reach to 1.6 MPa, the expansive rate is above 11%, and the compressive strength is basically stable under the condition of soaking in water for 90 days. The result of microscopic analysis shows that the effect of the SAP is to form the amorphous phase condensate particles, which is a kind of the complex condensate filling material. The main function of the GPA is to introduce the gas phase cavity in the filling body, and the HA is mainly used to form the hydrophobic effect on the surface of the filling body, so that the filling body can be resistant to water for a long time.