Abstract: The filling expansion mechanism and control measures of high concentration slurry in goaf is one of the difficult problems to be solved in the filling treatment of cavity goaf. Based on this, combined with the high concentration slurry transportation and rheological theory, a high concentration slurry filling process model was constructed to reveal its expansion mechanism, the dynamic and resistance calculation methods of filling expansion process were studied, the main influencing factors and control methods of filling accumulation body morphology were determined, and the theoretical results were verified by outdoor filling test.The results show that the the relative error between the calculated value and the experimental value of high concentration slurry filling resistance is about 5%; the rheological parameters yield stress and viscosity of slurry are directly proportional to the pipeline transportation resistance; the strength growth trend of slurry accumulation body is affected by the setting characteristics, and the resistance of slurry flowing between the accumulation body and the roof increases during the condensation process; when the filling material and flow rate remain unchanged, the resistance along the pipeline transportation is mainly affected by The results show that the local resistance is related to the pipe diameter, elbow, diameter change form and quantity, and the more the number, the greater the local resistance; the slurry property, filling path and grouting technology are the main factors affecting the shape of filling accumulation body. Shortening the filling distance, reducing the number of pipe diameter and elbow, reducing the yield stress and viscosity of slurry, and increasing the grouting flow and pressure are helpful The results provide a basis for the controlled filling of high concentration slurry in cavity goaf.