The invention relates to an automatically detecting machine for an antirust coating in a pipeline, which belongs to the field of thickness measurement and detection for a metal surface coating. The automatically detecting machine comprises a detecting machine head, a drive machine body and a wireless remote controller, wherein the detecting machine head consists of a rotating part of a front half part and a fixed part of a rear half part; the rotating part of the machine head consists of a front camera, a lateral camera, an illuminating lamp and a thickness gauge; the fixed part of the machine head consists of a motor, a speed reducer, a hollow shaft, a shaft bush, a gear and an inner toothed ring; and a walking motor, a contracting brake, a speed reducer, a gear box and a driving wheel of the machine body part are arranged on the rear half part, and an on-board remote control box, a battery set and a driven wheel are arranged on the front half part. The automatically detecting machine is wirelessly and remotely controlled to walk in a pipe so as to detect coating defects and measure the coating thickness, and wirelessly transmits real-time images to a display outside the pipe, thereby achieving the man-machine conversation. The whole automatically detecting machine has compact structure, reasonable arrangement, smooth operation, reliable working and high automation efficacy. The automatically detecting machine is integrated pipeline construction innovative equipment of machinery, electron, communication and optics and has popularization and application prospects.