Prefabrication and assembly construction technology is more and more widely used in bridge construction because of its advantages of green environmental protection, convenient construction and controllable quality. Based on the project of national highway 329 smart expressway, this paper puts forward a new construction method of front supporting and rear anchoring based on the original prefabricated and assembled bent cap construction method, and studies the internal force of the whole construction process of the two methods through numerical analysis and comparison. The research shows that: (1) In the construction of front support and rear anchor, the internal force distribution of the capping beam is similar to that of a simply supported beam under the conditions of lifting the capping beam and front support, while the internal force distribution is similar to that of a cantilever beam under the conditions of removing the crane; (2) The structural internal force of the capping beam during the whole construction process of the front supported and rear anchored construction method is significantly less than that of the rear anchored construction method due to the synergistic effect of the front supported and the rear anchored. Especially when the crane is removed, the maximum bending moment of the capping beam is reduced by 73%, indicating that the front supported and rear anchored construction method have greater safety; (3) The maximum tensile stress of the bent cap in the whole construction process is only 1.2MPa, which is less than the design value of the axial tensile strength of the concrete of 1.83 MPa, indicating that the bent cap is always safe and reliable in the installation process. The proposal of front supported and rear anchored construction has important guiding significance for the innovation and development of construction technology of spliced bridge substructure.