Abstract: Taking the gangue gypsum filling material composed of Helanshan coal gangue as the research object, the mechanical properties and macro-meso structural damage of the paste material were studied. In this paper, according to the relationship between the fine gangue rate of coal gangue (the fine particle content of coal gangue below 5 mm) and the strength of paste specimen, the ratio range to meet the needs of Baijigou filling mining project is studied. The PFC software was used to study the mesoscopic failure of the filling body, and the influence of mesoscopic parameters on the macroscopic characteristics and mesoscopic structure of the filling body was analyzed. The failure process was inverted by the discrete element PFC software to study the bearing performance and damage mechanism of the paste filling body. Exploring the meso-level characteristics of paste filling body is helpful to better understand the variation law of meso-structure of filling body and establish the relationship between meso-level characteristics and mechanical properties of filling body. The in-depth study on the preparation process and working performance of gangue gypsum filling materials can provide important theoretical basis and practical reference for the rational application of coal-based solid waste and the safe and green development of coal resource mining technology in the future.