The invention discloses a reinforcing support for an automobile threshold and an automobile lower floor. The reinforcing support comprises a frame body, a supporting structure and a plurality of connecting pieces. The supporting structure is connected in the frame body. The multiple connecting pieces are arranged along the frame body. The frame body and the supporting structure are both connected with the connecting pieces. The invention further discloses a reinforcing structure for the automobile threshold and the automobile lower floor. The reinforcing structure comprises the threshold, a floor lower longitudinal beam and the reinforcing support. The threshold is arranged above the floor lower longitudinal beam. The reinforcing support extends in the length directions of the threshold and the floor lower longitudinal beam. The upper portion of the reinforcing support is connected with the side face of the threshold through the corresponding connecting pieces, and the lower portion of the reinforcing support is connected with the side face of the floor lower longitudinal beam through the corresponding connecting pieces. The overlapping mode is simple, site operation is easy, the structural strength of a threshold and lower floor area can be improved easily, and the electric safety performance of a passenger compartment and the automobile is improved.