The invention relates to an active magnetic bearing using a bias magnetic flux commonly in radial direction and in axial direction. A bias magnetic current in an axial control coil provides a static bias magnetic flux for the radial direction and the axial direction to generate static bearing capacity, the control current in the axial control coil and in a radial control coil provides the controlmagnetic flux to respectively generate dynamic levitation force in radial direction and in axial direction, and external disturbance is overcome to ensure that a rotor levitates stably at a balance position of the radial direction and the axial direction. A bipolarity switch power amplifier is adopted in axial direction, a CRPWM current following inverter is adopted as a power amplification circuit in radial direction, an eddy current displacement transducer is adopted to detect axial displacement and radial displacement of the rotor and feed the axial displacement and radial displacement back to a DSP controller which is used for carrying out PID operation and providing a corresponding control signal for the power amplification circuit after processing, and the power amplification circuit generates control current in a magnetic bearing coil to realize stable levitation of the rotor in axial direction and in redial direction. The active magnetic bearing of the invention has the advantages of small volume, low power amplifier cost and high radial bearing capacity.