Abstract: The present invention provides an apparatus and a method for ranging, following and positioning of a mobile device. The apparatus includes an emitting unit, a receiving unit, and a computing unit. The emitting unit and the receiving unit are connected to the computing unit. The emitting unit is configured to emit a centimeter wave to an object to be followed. The receiving unit is configured to receive the centimeter wave. The computing unit is configured to calculate a distance between the mobile device and the object to be followed according to a time difference between emission of the centimeter wave and reception of the centimeter wave, and further calculate a movement distance according to the distance and a threshold distance difference. The present invention can be made waterproof and oil resistant. Compared with the technology using laser, the present invention better prevents measurement failure caused by permeability of the medium.