5倍。Based on the Nano-CMM structure, error distribution characteristic and accuracy demand, the micro three light beam planar reflector laser interferometer was selected to separate the Nano-CMM error. The error separating device was designed to realize the accurate adjustment of parallel move, beat, pitch and height, and the horizontal angle between the reflectors. The influence on the measurement result of the interferometer, which is created by using the 45 degree reflector to deflect the beam, was analyzed on principle. The error separating results indicate that the single-time separating of the standard indicating error and the deviant, pitch and beat error of the guide strip can be realized by the device. The additive error created by the heat, vibration and non real-time measurement of the common instruments is decreased via the error separating device. The error correcting precision using this method is five times more than that of the ordinary method. 