In this paper, we propose a method of subdivision surface quality assessment by reflection lines on programmable graphics hardware (GPU). Using reflection lines is effective for surface quality assessment because the shapes of these lines are changed according to a slight variance of surface shapes. This fact also implies that reflection lines should be calculated precisely. We introduce an intuitive, fast and robust approach for calculating reflection lines by using a plane light source texture based on a fragment program of recently introduced GPU. In addition, we describe a method of calculating position and normal of subdivision surfaces for each fragment on GPU. As our framework for calculating reflection lines does not depend on the level of subdivision, a precise assessment can be established even for low levels of subdivision polygons.