the main method to improve the resolution of optical system is to increase the aperture of the optical system, and it is a common method to use the sparse-aperture mirrors to obtain a large aperture primary mirror. the primary mirror of optical system is deployed when it is launched into the orbit, and the deviation between deployed position and design position determines the quality of the optical system. so it is necessary to analyze the position accuracy of segmented mirrors. sparse-aperture optical system is modeled by optical software zemax, and by adjusting six degrees of freedom of segmented mirrors can get curves between position error and image quality. the results show that different positions of segmented mirrors can produce different wave-front when they have same position error. moving along the z axis, the inner mirrors influence most while the outer ones influence smallest; tilt along the x axis, middle ones have maximum wave-front aberration while the outer ones produce minimum wave-front aberration. when tilt along y axis, middle segmented mirrors have the smallest wave-front aberration and outer ones have maximum. two methods are used to distribute the wave-front aberration onto each segmented mirror. one is that according to the relationship curves, distribute the position error to each segmented mirror alone. another is that each one has same position errors. the final result shows that the former method has a more relax position error when generates the same wave-front aberration. © 2017 elsevier gmbh