The invention discloses roll-on device and method for a large fixed type rotary crane, which is characterized in that the roll-on device mainly comprises two groups of hoists, two groups of rigid gantries, four running trolley groups, eight jacks, a regulation poppet and a wheel-sided brake, wherein each rigid gantry consists of a shoulder bracket welded on the main body of a crane, support columns connected with the shoulder bracket and a sill beam arranged below the gantry legs, and the sill beam is connected with a support bracket welded on the main body of the crane through bolts; and each running trolley group comprises an upper equalizer, an intermediate equalizer, a trolley and hinged shafts of various grades. The two groups of the rigid gantries are symmetrically installed on two sides of the main body of the crane, the four running trolley groups are connected with the regulation poppet through bolts and bolted below the rigid gantries, the eight jacks are symmetrically installed between the gantries and the trolley groups, the two groups of winches are respectively arranged on the front and the back of the main body of the crane, and during rolling on, the winch at one side draws to move the main body of the crane, and the winch at the other side plays the role of braking. Through regulating the jacks, the regulation poppet is withdrawn so as to ensure that the main body of the crane is in position for installation.