The invention discloses an automatic opening device for the pavement of an underground power cable. The automatic opening device comprises a machine body; a first pipe inlet trough is formed in the machine body; a pipe outlet correspondingly communicated with the first pipe inlet trough is also formed in the machine body; first drill pipes and second drill pipes sliding in the first pipe inlet trough are arranged in the first pipe inlet trough; a drive pipe rotating in the pipe outlet is arranged in the pipe outlet; a first pipe cavity is formed in the drive pipe; the first pipe cavity, the first drill pipes and the second drill pipes are in polygonal arrangement; a first power cavity comprises a pressure shaft, and a pressure end head correspondingly and rotationally connected with the first drill pipes and the second drill pipes is connected to the end part of the pressure shaft; as a traditional drill pipe can be arranged into a plurality of sections of first drill pipes and second drill pipes, the operation and the control of the first drill pipes and the second drill pipes is further facilitated, and the transportation of the first drill pipes and the second drill pipes is further facilitated, so that the working efficiency is improved.