A dual displacement measurement meter applied as a compensatory device for spindle thermal growth compensation , it can reduce the measurement error dramatically from single measurement device. The result matches the laser inspection report, which is an external direct checking device and been considered as one of the best checking device of spindle thermal growth. However, the non-flat surface of spindle nose, fluctuating measurement distance and the tiny measurement meter can hardly be fitted rectangular to spindle nose surface which create a certain percentage of error when the single displacement measurement meter is applied. The addition of a differential amplifier will greatly enhance the linear output voltage fed back from dual measurement meter to the CPU and provide a high sensitive level of compensation. This new device can reduce the measurement error from 6% down to 1.8%. The machining tolerance can be improved greatly and machining time is reduced. The quality of the machine and the cutting performance can be upgraded.