The invention relates to a car body front floor strengthening structure. The car body front floor strengthening structure is used to improve rigidity of a car body and improve crash safety performance, and simultaneously the novel structure reduces the weight of the car body by removing a part of components. The car body front floor strengthening structure is characterized in that a left enclosed frame structure and a right enclosed frame structure are formed respectively through an upper longitudinal beam of a floor and a cross beam of a seat, and through a threshold and a middle gallery, a left enclosed circle structure and a right enclosed circle structure are formed respectively through a lower longitudinal beam I of a front floor, a lower longitudinal beam II of the front floor and the threshold, and the middle gallery and a cross beam of a rear seat (or a rear floor), not only can all the structures improve torsion and bending rigidity of a whole car, but also can the upper longitudinal beam of the floor, the lower longitudinal beam I of the front floor and the lower longitudinal beam II of the front floor respectively transmit crash force transmitted from a front longitudinal beam to the rear of the car body through three paths, and accordingly integrality of a passenger compartment is guaranteed. Kickdown and a reinforcing plate of the front floor are removed on the premise of using the lower longitudinal beam I of the front floor and the lower longitudinal beam II of the front floor, and the weight of the car body is indirectly reduced, and furthermore power economical efficiency of the whole car is improved.