This paper analyzes the necessity for the calibration of LDA system. Proposing a newconcept of using a known definite speed of a single particle as velocity reference, according to that an unique rotating disk for calibrating LDA system (calibrating disk ) is specially designed. It is verified experimentally that both stability of rotating speed and accuracy of linear velocity of this calibrating disk system have achieved or exceeded the desire of designing parameters. Therefore, linear velocity of calibrating disk can be considered as a reference velocity to make comparison with the velocities and evaluation measured by an LDA system or other optical anemometers.