A diesel engine runaway control device comprises an oil inlet joint (1), a nonmagnetic connection guide pipe (2), an inductance coil (3), a permanent-magnetic ring (4), an inner magnetic valve block (5) and an oil outlet joint (6). The device is in a three-step tubular structure integrally, the right end of the device is provided with the oil inlet joint (1) which is provided with an internal thread, the left end of the device is provided with the oil outlet joint (6) which is provided with an outer hexagon and an external thread, the inductance coil (3) is positioned on the left side of the middle portion of the device, the permanent-magnetic ring (4) is sleeved onto the nonmagnetic connection guide pipe (2), can slide horizontally and is positioned on the left side of the inductance coil (3), the middle diameter of a central through hole is larger than the diameter of two ends of the central through hole, and the inner magnetic valve block (5) is mounted inside the central through hole and can slide horizontally. The diesel engine runaway control device is simple in structure, easy to manufacture, convenient to operate, safe, reliable and capable of terminating runaway accidents of a diesel engine quickly and timely and prolonging the service life of the diesel engine, so that safe and reliable running of equipment and normal operation of oil drilling are guaranteed.