The utility model discloses a frost-damage preventing drainage system for tunnels. A heat-insulation embedded ditch (6) is arranged under a primary support layer (1), multiple drain pipes (7) are disposed in the heat-insulation embedded ditch (6), an inspection well (8) is arranged between each two adjacent drain pipes (7), and the lower ends of the inspection wells (8) are communicated with the drain pipes (7). Waterproof plates (11) are paved between the primary support layer (1) and a secondly lining concrete layer (2), an annular perforated corrugated pipe (12) and a longitudinal perforated corrugated pipe (13) are arranged outside the waterproof plates (11), and an opening at the lower end of the annular perforated corrugated pipe (12) is positioned in a macadam permeable layer (10). By the frost-damage preventing drainage system, drain pipes of tunnel drainage systems in cold area can be prevented from being frosted and blocked, damages to the tunnel lining structure are avoided, travel safety is guaranteed, and cleaning and maintenance expenses during operation are lowered greatly. The frost-damage preventing drainage system for the tunnels has the advantages of simple structure, easiness in implementing and popularization, high reliability, and the like.