The present invention discloses a single-drive bidirectional-crawling pipe-cleaning robot, including a front body assembly, a transmission assembly, and a rear body assembly. The transmission assembly is driven by a single power source, and a transmission effect of a connecting rod mechanism, a gear mechanism, and an equal-dwell cam mechanism is used to implement alternate retraction and support of the front body assembly and the rear body assembly in a radial direction and a telescopic motion in an axial direction between the front body assembly and the rear body assembly and at the same time implement synchronous rotation of a dredging cutter head, so as to implement bidirectional crawling and pipe cleaning work of the robot along a pipe. The present invention is stable, reliable, compact, and practical, and implements single-drive bidirectional crawling and pipe cleaning in a pipe having a greatly changing pipe diameter, so that the obstacle negotiation performance and adaptability to pipe diameter changes of an in-pipe robot are effectively improved, the endurance of the in-pipe robot is improved, and practical engineering significance in cleaning of a horizontal pipe having a greatly changing pipe diameter is provided.