The invention relates to a method for an extra heavy-loaded vehicle to cross a multi-span continuous beam bridge. The method includes the following steps that a, steel oblique cushion blocks, auxiliary steel boxes, rubber cushion blocks, bridge crossing steel boxes and steel cushion beams are prepared; b, before the extra heavy-loaded vehicle crosses the bridge, traffic is interrupted, and the steel cushion beams are laid on a bridge floor at intervals in the width direction of the beam bridge; c, two lines of the continuous bridge crossing steel boxes are erected on the steel cushion beams inthe length direction of the beam bridge; d, the auxiliary steel boxes are laid on the bridge crossing steel boxes at intervals, and the rubber cushion blocks are placed between the bridge crossing steel boxes and the auxiliary steel boxes; e, the steel oblique cushion blocks are connected with the bridge crossing steel boxes and the auxiliary steel boxes in an obliquely-erected mode, and the bridge crossing steel boxes, the auxiliary steel boxes and the steel oblique cushion blocks form two routes for the extra heavy-loaded vehicle to pass; and f, the extra heavy-loaded vehicle crosses the beam bridge at a low speed, and after the extra heavy-loaded vehicle crosses the beam bridge, the steel oblique cushion blocks, the auxiliary steel boxes, the rubber cushion blocks, the bridge crossingsteel boxes and the steel cushion beams are detached, and normal traffic is recovered. The method is low in cost and convenient to construct. The invention relates to the technical field of bridge engineering.