A face angle testing device of a rotary tool comprises a well deviation calibration table frame, a rotary testing table frame, an orientation calibration table frame, a power supply module, a microcomputer module, a slip ring wire and an emergency brake; a rotary tool face angle testing and control system is installed on the rotary testing table frame and is driven to rotate by a direct-current deceleration motor on the rotary testing table frame, then the rotary testing table frame is fixed to the well deviation calibration table frame, and finally the well deviation calibration table frame is fixed to the orientation calibration table frame; and power is supplied to the whole rotary testing table frame by the power supply module through the slip ring wire, and after collected signals such as well deviation, orientation, the rotation speed and the tool face angle are regulated by the rotary tool face angle testing and control system, the signals are transmitted to the microcomputer module through the slip ring wire, so that data and control communication between the rotary testing table frame and the externally-connected microcomputer module is achieved. The face angle testing device of the rotary tool supplies powerful technical guarantee to the processes of accurate measuring, measured influence factor analyzing and accurate control achieving of the rotary tool face angle system under the rotary working condition.