GPS技术虽然已广泛应用于隧道平面控制测量，并显示出极大的优越性。但是，如何将以法线为准的地表GPS成果改换到与以垂线为准的洞内导线测量相符合，从而解决好垂线偏差对隧道贯通精度的影响，是一个值得探讨的问题。根据垂线偏差的基本理论及其对隧道贯通测量的影响因素，结合工程实例，提出了用GPS建立隧道控制网时，垂线偏差对横向贯通测量影响的规律和解决途径。

GPS technology has been widely used in the plane control survey of tunnels and has exhibited great advantages. However, it is one of the topics worthy of study that how the results of GPS survey that is based on the normal line can be converted to be compatible with the traverse survey inside tunnels that is based on the plumb line, so as to minimize the influence of the plumb line deflection on the transverse breakthrough accuracy of tunnels. On basis of the basic theory of the plumb line deflection and the influence factors on the breakthrough survey of tunnels, the paper, taking works cases as example, presents the rule of the influence of the plumb line deflection on the transverse breakthrough survey and the corresponding countermeasures when GPS is used to establish the control net works of tunnels.