The invention discloses a mud and sand separating device for water conservancy projects. The mud and sand separating device comprises a base frame and a plurality of rotational flow sand removal devices; the base frame comprises a base plate, supporting rods, fixing plates and a storage tank; the base plate is horizontally arranged, and the longitudinally-arranged supporting rods are distributed on the bottom surface of the base plate; the top end of the storage tank is open, and the storage tank is horizontally located above the base plate; the storage tank is fixedly connected with the top end of each supporting rod, and the fixing plates are horizontally arranged between the multiple supporting rods; the rotational flow sand removal devices are longitudinally arranged and fixedly connected with the fixing plates, and a water pump and a first mud pump are arranged on the base plate; a top plate is horizontally arranged above the storage tank, and high-pressure spraying heads are distributed on the bottom surface of the top plate and used for spraying water into the storage tank; and the water discharging end of the water pump is connected with a water conveying pipe which communicates with the water feeding end of each high-pressure spraying head. The mud and sand separating effect is good, the separating efficiency is high, manpower is saved, and operation is convenient.