To study the microscopic damage characteristics of crack tip in the three-point bending process of hydroxyl-terminated polybutadiene(HTPB) propellant, the dynamic damage process of crack tip was observed by scanning electron microscopy. Based on submodel of propellant, a multi-scale model of three-point bending process was established. The macroscopic deformation and meso-damage of crack tip during three-point bending process were calculated. The damage process of crack tip was analyzed by experiment and numerical simulation, respectively. The results show that the damage process of the three-point bending test is firstly the dewetting of the particles at crack tip, and then from the damage zone. With the increase of the compression displacement, the microcrack caused by the dewetting of different particles converges with crack tip to make the crack develop. Due to the tensile action at both sides of the crack, the crack tip becomes blunt. As the compression displacement increases from 0 to 1.2 mm, the crack opening displacement increases from 0 to 84.1 μm, and the increase rate is also increased. The numerical simulation results agree well with the experimental results. The multi-scale numerical model based on submodel can effectively simulate the macroscopic deformation of propellant on three-point bending process and the microscopic damage process of crack tip, which provides a new method for the analysis of macroscopic and microscopic damage process of propellant.