The invention discloses a vertical-shaft driving device of a centrally-driven mud scraper and relates to a driving device of a centrally-driven mud scraper for a sedimentation tank in a sewage treatment plant. The driving device comprises a piston push rod, a support seat of the piston push rod, a ratchet mechanism and a rotary support seat with a ratchet wheel, wherein the ratchet mechanism consists of a rotary arm, a pull spring and a ratchet; one end of the rotary arm is fixed on a central shaft of the rotary support seat with the ratchet wheel, and the other end of the rotary arm is hinged with the piston push rod on the outer side of the ratchet wheel; the ratchet arranged on the rotary arm is prepressed onto the surface of the ratchet wheel through the pull spring; and one end of the pull spring is fixed on the rotary arm, and the other end of the pull spring is fixed on the ratchet. The device has a simple structure, a small number of machine members, high work efficiency, adjustable speed and low energy consumption, does not generate noise, runs stably and is easy to maintain.