Provided are a magnetic tag sensor and a manufacturing method therefor, and a riverbed scouring measurement device. The magnetic tag sensor comprises: a cylinder (1), wherein a threaded pipe (2) is embedded in a wall of the cylinder (1), and the threaded pipe (2) is used for simulating a magnetic dipole; two wiring ports (3, 4) of the threaded pipe (2) are respectively connected to a first cable and a second cable, and penetrate an outer wall of an upper cross section of the cylinder (1) to extend out of the cylinder (1); the cylinder (1) is sleeved on a guide rail (5), and the cylinder (1) is arranged at the junction of a riverbed and water; a tail end of the guide rail (5) is inserted into the riverbed, and a water sealing box (6) is mounted at the top of the guide rail (5); and a power source module (7), a relay (9) and a load (8) are arranged inside the water sealing box (6), with the first cable being connected to a positive pole of the power source module (7), and the second cable being connected to a negative pole of the power source module (7) by means of being connected to the relay (9) and the load (8) in series; and the threaded pipe (2) in the wall of the cylinder (1) moves up and down with the riverbed to generate a magnetic field signal.