Transverse moving flat car of portal crane and transverse moving method

The invention provides a transverse moving flat car of a portal crane and a transverse moving method, and solves the problems of reassembly, prolonging of the construction period and increment of the cost in transverse movement of the portal crane from one set of operation rails to the other set of operation rails or even multiple sets of operation rails. The transverse moving flat car of the portal crane comprises a connecting beam, two walking mechanisms, two jacking systems, a rail bracket and a walking mechanism traction device; the two walking mechanisms are positioned at two ends of the connecting beam, and are connected through the walking mechanism traction device; the walking mechanisms can linearly move back and forth along portal crane operation guide rails; the two jacking mechanisms are positioned on the inner sides of the two walking mechanisms; one ends of the jacking mechanisms are arranged on the rail bracket; the rail bracket is matched with transverse moving flat car operation guide rails;