The revolved concave surfaces are widely applied to both optical equipments and aerodynamic domain. The revolved surface is measured by digitized measurement with the coordinate measuring machine (CMM) in this paper. A CMM inspecting path planning which is different from traditional measuring method for revolved surface is given. An automatic algorithm of digitization on a CNC coordinate measuring machine for an unknown revolved surface is present. At the same time, this method is proved effectiveness through a practical measuring example of an optical part. The Measuring process and the measuring results are illustrated in detail.