Abstract: Taking the segment rings of shield tunnel of Shanghai Metro Line 13 as a study case, the initial structure of segment rings with the worst waterproofness under various error cases is determined. The decrease of waterproofness is quantified through change of convergence of segment ring as its waterproofness fails. The results indicate that the radial erection error of segments causes the joint dislocation and external opening of waist joints simultaneously, and the latter is worse to the initial waterproofness than the former. As the waterproofness fails, the convergence of segment rings with the worst waterproofness in one joint error case is 1.53‰D, it is less than a half of that in the no error case, and the convergence further decreases as the number of erroneous joints increases. If there are more than three erroneous joints, the waterproofness of segment rings with the worst waterproofness will fail before they come out of shield rear. According to the above conclusions, some recommend actions are proposed for the quality control of segment erection during construction phase and the waterproof monitoring of segment rings during service phase.