The invention relates to a railway bridge beam replacement system, an assembly process and a beam replacement process, which comprises an existing component, an existing beam to be replaced, an existing railway rail laid on the existing beam, an existing bridge pier installed on the ground, an existing bearing arranged on the existing bridge pier and located below the existing beam; A beam changing device for replacing an existing beam with a new beam of a steel-concrete composite T-beam structure; Which comprises a strip foundation installed on a highway road under an existing beam and takinga steel pipe as a module and pouring concrete inside, a spacer film disposed between the strip foundation and the hardened foundation, The lower end of the steel bar implanted in the foundation and welded with the module is connected with the steel pipe flange and the strip foundation by adopting the anchor bolt and adopts the support system of the steel pipe erection, and the synchronous translation system arranged on the upper end of the support system is reasonable in design, compact in structure and convenient in use.