The invention discloses a water-injecting efficient mud scraper with automatic water injection, comprising a service bridge, a driving mechanism, a rotary shaft, a mud scraping mechanism, and an end cover, wherein the mud scraping mechanism includes a mounting frame and a scraper plate, front and back sides the scraper plate are provided with water injection guns, each water injection gun has a control switch that controls its turning-on/turning-off; a protective cover is arranged outside the water injection guns and includes a main portion and an end portion, and the main portion has a chamber for mounting the water injection guns; the end portion is provided with a main linear chamber and an auxiliary linear chamber, a compression spring is mounted at the bottom of the main linear chamber, and the auxiliary linear chamber is communicated with a cavity of the main portion; one end of the end cover is provided with a main protrusion portion and an auxiliary protrusion portion; the main protrusion portion extends into the main linear chamber and abuts to the compression spring; the auxiliary protrusion portion is extended from the auxiliary linear portion into the cavity and connected with the control switches. The water-injecting efficient mud scraper is low in energy consumption and long in service life and allows the water injection guns to automatically turned on/off.