The utility model relates to an automobile inner structure especially relates to a back sub vehicle frame swing arm installing support device. This back sub vehicle frame swing arm installing support device, install the arm including link and the swing arm that is located the link both ends, the link includes frame upper cover plate and frame apron down, be provided with on the swing arm installation arm with the swing arm of swing arm articulated before the mounting bracket and with the swing arm of swing arm articulated after the mounting bracket, swing arm installation arm is provided with the location reinforcing plate with the junction of link, the location reinforcing plate includes the first connecting plate of fixing with the link laminating, with the fixed second connecting plate of swing arm installation arm laminating, a third connecting plate for connecting first connecting plate and second connecting plate, the section of location reinforcing plate is " U " shape. The utility model discloses have can connect the swing arm with back sub vehicle frame cavity, effectively slow down impact force, reinforcing overall structure intensity that back sub vehicle frame cavity received, avoid beneficial effect such as back sub vehicle frame fracture.