The invention relates to a mud suction nozzle of a submarine pipeline ditcher. The mud suction nozzle comprises a mud suction nozzle steel pipe, and the lower portion of a mud outlet of a mud suctionmain pipeline is externally covered with a sealed air cabin chamber and a water cabin chamber from top to bottom in sequence, and the air cabin chamber communicates with a high-pressure air conveyingpipe; and a plurality of air outlet holes are evenly formed in the pipe wall of the mud suction nozzle steel pipe located in the air cabin chamber along the perimeter, and high-pressure air is sprayedout through the air outlet holes to achieve mud suction. The water cabin chamber communicates with a high-pressure water pipe, four boron carbide nozzles are evenly distributed at the water cabin chamber bottom located on the outer side of the mud suction nozzle steel pipe, and the water outlet direction of the boron carbide nozzle is opposite to the mud suction direction. The mud suction nozzleis firm and durable, and cannot be broken, the problem that a mud suction opening is buried and blocked can be solved conveniently and fast, and the construction efficiency and safety of pipeline deepburying are improved.