In order to study the retaining mechanism of gangue filling space in double-shield solid filling mining, the geometric model of retaining filling space was established by combining theoretical analysis with EDEM numerical simulation. The influence of filling height, multi-frame sequential blanking process and blanking step on the accumulation state of filling body was simulated. The results show that the filling operation and space enclosure model in double-shield solid filling mining are established, and the calculation method of filling body volume is obtained. The relationship between filling volume and working face length, support center distance, filling step distance, filling height, gangue rest angle, length of blanking port and length of blanking port is obtained. The annual filling amount of gangue under two kinds of double-shield solid filling mining height and filling height in Hecaogou Coal Mine is calculated theoretically. The increase of filling height will significantly increase the accumulation range, and the filling height has little effect on the accumulation angle of gangue particles. When the filling height increases from 1.0 m to 1.2m, the diameter of gangue accumulation range increases from 3.32m to 3.82m, and the accumulation angle increases from 28.7 ° to 28.9 °; The numerical simulation of the blanking process along the working face and the blanking step along the advancing direction of the working face verifies the rationality of the filling space maintenance geometric model of the double-shield solid filling mining proposed in this paper, and verifies the existence of ' gully ' and ' gully ' in the filling process, which provides a theoretical basis for the efficient process design of double-shield solid filling.