The utility model relates to a drainage tunnel for ditch water treatment. The utility model discloses a tunnel body, the bottom of tunnel body is equipped with the partition wall along tunnel body length direction for the tunnel body forms two water channel, and the import of tunnel body is provided with the lock chamber, is provided with the twice gate in the lock chamber, and the gate is corresponding one by one with water channel. The utility model discloses during implementation, drainage in flood season tunnel normally overflows, and overhaul dry season, during the maintenance, overhaul earlier down the gate of one side, rivers overflow one side from the partition wall in addition, treat this side and overhaul the back that finishes, mention this side gate again, and one side gate in addition carries out drainage tunnel mid -board and overhauls one side in addition down. The utility model discloses can conveniently examine and repair, just adopt single tunnel structure, the cost is hanged down, easy to carry out, the ditch water treatment drainage tunnel that be particularly useful for overflowing for a long time, the flow differed great withered flood season phase.