In order to accurately describe the generation, migration and collapse of foam in fractured-vuggy reservoirs at 140°C and 30 MPa for dynamic analysis, this study utilized a self-designed visual fracture-pore model to achieve intuitive capture of foam dynamics. Through conducting nitrogen foam flooding experiments, the morphology and evolution laws of foam were quantitatively characterized. Nitrogen foam flooding experiments were conducted to quantitatively characterize the foam morphology and its evolution. The results show that under pressurized conditions, the half-life of the foam is significantly longer than that under normal pressure conditions. The change in the half-life of the foam is not obvious under low-pressure conditions (5 MPa) compared to high-pressure conditions (30 MPa). Therefore, low-pressure conditions can be used to simulate high-pressure conditions. In fractured-porous reservoirs, when the ratio of fracture width to foam size (W/D) is approximately 1.1 times, the roundness and size distribution of the foam are moderate. The bubbles are completely separated by the liquid film, the foam is distributed in a discrete manner, and it accumulates in an "elliptical" shape. When the W/D ratio is increased to 2.5, the size range of the foam becomes concentrated and it accumulates in a "spherical" shape, exhibiting strong stability and blocking capacity. when the W/D ratio is reduced to 0.5, the foam is strongly compressed by the crack walls and cannot exist in the form of discrete bubbles. The size and roundness variations are significant, and it accumulates in a "single flat ellipsoidal" form. The research shows that in fractured-porous reservoirs, the presence form of bubbles is time-dependent. The shape and stability of the bubbles are closely related to the fracture width and bubble size. When the crack width is greater than 2.5 its size, it generates smaller and more stable foams, and thus effectively seals the crack channels. This study has revealed the time-varying occurrence patterns and critical size matching principles of foams in fracture-pore reservoirs, providing a crucial theoretical basis for the performance optimization of efficient foaming agents in fault-hole type reservoirs and the precise optimization of foam size.