An initial turntable calibration method based on coordinate transformation was proposed to improve the target tracking precision of a vehicle-borne tracking system. First, according to the coordinate transformation theory, a precise turntable calibration model was established and a transformation matrix for the turntable calibration was obtained. Then, an approximate calibration approach based on the practical need was derived with reasonable analysis and careful approximation. Finally, a combined calibration method by using both approximate calibration and precise calibration was implemented in the turntable initial calibration process for a practical vehicle-borne opto-electronic tracking system. Experimental results show that the combined calibration method can improve the efficiency of turntable initial calibration. After precise calibration, the tracking error of the turntable is smaller than 0.1° for a remote target larger than 10 km away, which completely satisfies the precision requirements of the vehicle-borne opto-electronic tracking system. This calibration method has been successfully used in several vehicle-borne opto-electronic tracking systems.