Disclosed is a dual-functional resonant based magnetic field sensor that functions as magnetic field sensor and accelerometer, respectively, comprising a sensor structure including a mass block and motion sensor electrodes, capacitance to voltage converter and amplifier to convert sensing signals of the sensor electrodes into voltage, as output signals of the magnetic field sensor, a driving circuit to provide the output signals to the mass block in the form of current, to drive the mass block to vibrate, and a selection circuit to select measurement of magnetic field or acceleration. The driving circuit may be a comparator. The selection circuit may be replaced by a filter to select frequency bands of the output signals of the converter, for simultaneously providing signals representing magnetic field and acceleration, respectively.