The space resolution of stereo vision system affects the accuracy of the measurement. The space resolution differs at different points and in different directions at the same point. Based on the formula of the stereo vision system, the space resolution of all the points is calculated and analyzed in observation field. The results show the space resolution is the highest with axis angle between 80°and 100°. And the space resolution in the X direction is higher than that in the Y direction. The experiment result is similar to the analysis result. Finally, we get the best structural parameters of stereo vision system according to the space resolution.