The invention discloses a tunnel crystallization prevention method. The tunnel crystallization prevention method comprises the following steps: (1) preventing newly excavated tunnels: smearing anti-contamination coating on inner walls of drainage blind pipes of the tunnels, and installing a U-shaped sealer at the end of each drainage pipe; (2) governing a completed tunnels: for the tunnels with dredging conditions, dredging the drainage blind pipes by using a dredging machine, after the dredging is completed, smearing the anti-contamination coating in the horizontal drainage blind pipes at a distance of not less than 1m from a water outlet of a side ditch, and installing U-shaped sealers at the ends of the horizontal drainage blind pipes; for pipelines without dredging conditions, perforating drainage holes at the water outlet of the side ditch, and installing drainage pipes in the drainage holes. The tunnel crystallization prevention method has the advantages that the crystallizationproblem of the tunnel drainage pipe can be effectively solved by virtue of the preventive measures for newly excavated tunnels and governing measures for the completed tunnels, and the safety, reliability, durability and operation service life of the tunnel structure can be guaranteed.