A new CNC lathe with a tandem table unit driven by two linear motors has been developed to machine the non-axisymmetric curved surfaces by turning. This lathe, which is equipped with four axes (X_1 X_2, Z and C), enables to realize the NACS-turning (Non-Axisymmetric Curved Surfaces Turning) , machine the 3D surfaces by turning synchronizing with the spindle rotational position. The key factors for this turning method is to realize precise tool trajectory for the commanded position even in high acceleration motion. In this method, the large inertia force caused by the rapid motion with high acceleration and deceleration is another problem. Therefore, canceling the innertia force, tandem tables for X axis are equiped on the CNC lathe. These two tables are controlled opposite direction to cancel the vibration transmission to the base and the sipindle. In this study, a new CNC lathe with 4 axes including a tandem table unit is introduced and the fundamental dynamic performances of the table motion of the CNC lathe are measured and evaluated. The effects of tandem tables during the motion control for the curved surfaces is also evaluated.