The invention discloses a magnetic measurement positioning device, which comprises a packaging shell, wherein side guide wheels are respectively arranged on the upper portion and the lower portion of the packaging shell along the axial direction, a first three-dimensional fluxgate sensor is arranged on the upper portion of the packaging shell, a second three-dimensional fluxgate sensor is arranged on the lower portion of the packaging shell, the first and the second three-dimensional fluxgate sensors are respectively connected with signal collecting modules through wires, the signal collecting modules are connected with power supply and signal transmission cables which extend outside the packaging shell, and the distance between the first and the second three-dimensional fluxgate sensors is kept in constant. The invention provides the magnetic measurement positioning device and a method for monitoring slope deep displacement by utilizing the magnetic measurement positioning device can solve the problems that displacement values which meet monitoring accuracy requirement can not be calculated and more sensors are used, guarantee measurement accuracy of deep displacement, greatly reduce system cost, and is convenient in popularization and application.