This research describes an on-machine form measurement system of high precision ceramics parts. This system consists of a grinding machine and a laser displacement sensor. By using two horizontal axes of the grinding machine with sub-micrometric motion accuracy and the high precision laser displacement sensor which is mounted on the grinding machine, three-dimensional continuous form measurement with sub-micrometric accuracy can be realized in non-contact condition. In order to evaluate the stability and motion accuracy which influence the measurement accuracy of the system, the experiments to estimate stability and motion accuracy were conducted. And the form measurements were conducted.