The invention provides a containment system for type B independent liquid cargo tank. The liquid cargo tank comprises a top surface, a bottom surface and a side wall, wherein the top surface, the bottom surface and the side wall are formed by welding a plurality of outer plates; the containment system comprises leakage slots and liquid collecting wells; the leakage slots respectively cover all the weld seams among the outer plates on the top surface and the side wall; the liquid leaking from the weld seams can flow down along the leakage slots to an inner bottom plate of a hull; one or more liquid collecting wells are respectively arranged at both ends of the inner bottom plate in the length direction of the hull; insulating layers are laid on the top surface, the bottom surface and the side wall; the containment system also comprises a baffle plate; the baffle plate is arranged around the liquid cargo tank; and the upper end of the baffle plate is connected with the wall plate of the hull, and the lower end of the baffle plate is connected with the inner bottom plate. According to the containment system disclosed by the invention, the cost is reduced in the aspect of materials by reasonable design of the containment system, and the containment system can guarantee the safety of the hull structure in the case of liquid cargo leakage in the liquid cargo tank.