A plane microphone calibration device based on a free field comprises a sound source and a microphone fixing and rotating mechanism, and the sound source is fixed to a supporting rod through a sound source fixing mechanism and a sound source fixing mechanism fastener; the microphone fixing and rotating mechanism is fixed on a mounting base; the microphone fixing and rotating mechanism comprises arotating mechanism, the rotating mechanism is fixed on the mounting base, the upper end of the rotating mechanism is connected with a supporting rod-rotating mechanism connecting piece, the lower endof the precise scale circular ring supporting rod is connected with a supporting rod-rotating mechanism connecting piece, the upper end of the precise scale circular ring supporting rod is connected with a precise scale circular ring supporting frame, and the rotating mechanism drives the whole rotating control mechanism to rotate in a horizontal plane; a precision scale circular ring is installedon the precision scale circular ring supporting frame through a precision scale circular ring clamp a and a precision scale circular ring clamp b, and a calibrated plane microphone is installed in the center of the precision scale circular ring.