Abstract: In order to realize the recycling of phosphogypsum and phosphorus slag solid waste materials,and improve the utilization rate of industrial solid waste,the experiment uses phosphogypsum and phosphorus slag as the main raw materials,along with using water glass,cement clinker and phosphogypsum to jointly stimulate the activity of phosphorus slag for preparing phosphogypsum-phosphorus slag-based composite cementitious materials. The paper discuss the effects of phosphogypsum content,sodium silicate content,and phosphorus slag grinding system on the strength of phosphogypsum-phosphorus slag-based composite cementitious materials,while using SEM and XRD to analyze the microscopic structure and composition morphology of phosphogypsum-phosphorus slag-based cementitious materials hardened. The results showed that when the content of phosphogypsum is less than 50%,the strength of the composite cementing material at each age is inversely proportional to the content of phosphogypsum;when m(phosphogypsum) ∶ m( phosphorus slag) ∶ m( clinker) is 20 ∶ 72 ∶ 8,the sodium silicate content is 1. 5%,the 28 d compressive and flexural strengths of the cementitious material reach the maximum value of 43 and 6. 3 MPa. The grinding system will produce " micro-medium effect" ,which is beneficial to improve the strength of composite cementitious materials. The main hydration products of composite cementitious materials are C—S—H gel and ettringite. The ettringite and undissolved phosphogypsum are formed as the skeleton and was wrapped,filled and interwoven together by C—S—H gel to form a compact structure. When composite cementing materials are used to replace cement as filling materials in mining areas, the recommended phosphogypsum content is 20% ~ 40%.