In the paper, the strengthening and replacement of the sidewardmoving primary reinforcement structure of a shallowburied undercut tunnel is presented. Firstly, horizontal support elements and inclined support elements made of Ishaped steel are welded to the sidewardmoving primary reinforcement structure to improve its support capacity and portalshaped support structure are installed for tunnel portions within the scope of 4m away from the tunnel face. When all the temporary supports are installed, backfilling grouting is executed for the arch part of the tunnel. Finally, the sidewardmoving lattice girders are replaced and grouting is executed to improve the support capacity. During the full course of the treatment, monitoring and measurement are executed.