The invention provides a cable trench drainage structure and a cable trench construction method. The cable trench drainage structure comprises a water collection trench, a soakage pit and a connection pipe. The water collection trench is positioned at the bottom of a cable trench passing a road section; the soakage pit is positioned outside the cable trench passing the road section; the connection pipe is used for communicating the water collection trench with the soakage pit. Water accumulated in the cable trench passing the road section can be drained automatically.