Two-CCD binocular stereo vision systems are attracting research interest in many important fields such as 3-D coordinate measurement. However, accurate binocular system modeling is difficult because of lack of fundamental imaging formation theory. In this paper, we demonstrate how a binocular stereo vision system can be modeled, in order to measure a 3-D surface, by the invented skew ray tracing method to study the geometric relations between the images of the cameras and the 3-D surface. In order to investigate the overall accuracy and resolution of this system, the influence of infinitesimal camera reading errors on measured coordinate errors is determined by sensitivity analysis. Numerical verification demonstrates that the performance of the proposed system is excellent.