The multi-chamber arc extinguishing gap has attracted attention in lightning protection of distribution networks. During its operation, the arc sprays out and exchanges heat with air convection to form a gas jet, which forms a shear layer with the surrounding fluid velocity difference, which may evolve into a vortex ring structure, promoting gas cooling and insulation recovery after the arc. The formation of vortex rings is influenced by the chamber structure, and optimizing the structure can increase the probability of vortex ring formation and enhance the arc extinguishing effect. Therefore, the dissipation process of post-arc gas is observed by building a schlieren observation platform. The effects of chambers with different structure parameters on the formation of post-arc gas vortex ring and gas density recovery are investigated, and the effect of vortex ring on promoting post-arc gas cooling is analyzed. Based on the schlieren observation results, the formation process of post-arc gas vortex ring is simulated and analyzed by finite element simulation analysis software. It is proved that the reasonable setting of chamber outlet diameter can increase the probability to form post-arc gas vortex ring, and the vortex ring entrains ambient cold air into the hot kernel of the post-arc gas to promote the cooling and insulation strength recovery of the post-arc gas.