This study deals with non-axisymmetric curved surface turning (NACS-Turning) by a CNC lathe composed of a turning axis and two translation axes. NACS-Turning enables turning of a free surface such as cam profiles for internal combustion engines by synchronizing the X-axis with the rotation of the turning spindle. This novel machining method has possibility that productivity of workpieces with non-axisymmetric curved surfaces can be improved dramatically. However, accuracy is inadequate due to control delay and servo stiffness. Therefore this study tried improvement of accuracy by implementing an on-machine measurement system. In this report, the detail of the system is explained, and its effectiveness is confirmed.