In the traditional PMP calibration, the system calibration and phase measurement were performed dividedly, and the measurement result was the relative height to the reference plane. A fast calibration was proposed, in which two gauge blocks were used to replace the standard plane controlled by the mechanical shifting device in the traditional calibration, and fewer datum points were sampled from the surface of the gauge blocks to calibrate the system. With this method, both system calibration and phase measurement can be implemented simultaneously. The real height of the object relative to the supporting plane can be obtained when the supporting plane was not superposed on the reference. A cuboid block of normal height 14.00mm was successfully measured by this method. Its mean relative error was no more than 1.35% and the root-mean-square error was less than 0.15mm. The calibration of the PMP was simplified and became more flexible with the proposed method.