Abstract: When a truck-mounted howitzer is firing, the crew compartment structure deforms elastically under the influence of the muzzle blast load and causes disturbances in the internal flow field pressure within the cabin. The overpressure caused by these disturbances is one of the main factors threatening the safety of personnel and equipment inside the cabin. To meet driving requirements, the crew compartment of the truck-mounted howitzer is suspended on the chassis frame through an elastic support structure. At the same time, the stiffness and damping of the support structure are important factors affecting the deformation response of the cabin structure under the impact of the muzzle blast load. To investigate the effects of different cabin support conditions on the flow field Overpressure inside the Crew Compartment of a Truck-Mounted Howitzer, a foreign trade type of equipment was taken as the object. An entire path numerical model simulating the shock wave propagation from the cannon's muzzle to the interior of the cabin under extreme firing conditions was established. Systematic validation tests were conducted, covering data acquisition for overpressure in both the external and internal flow fields of the crew compartment, as well as the acceleration of the cabin structure. Based on the validated numerical model, simulations were performed to calculate the structural responses and internal flow field overpressures under eight different support conditions. The results indicate that although the cabin responds differently to changes in support conditions in different spaces, as the stiffness of the support structure for the truck-mounted howitzer cabin increases from small to large, the peak acceleration and velocity of the cabin structure significantly decrease, and the peak overpressure in the internal flow field also decreases. The presence of damping in the support structure significantly enhances the acceleration response of the cabin structure but helps further reduce its velocity response and lower the peak overpressure in the internal flow field of the crew compartment.