In view of an accurate evaluation of the security status of metro shield tunnel segments, based on the analysis of the formation mechanism of structural defects in metro shield tunnel segments, an evaluation index system is established from five aspects: segment deformation, water leakage, cracks, arch detachment, and material degradation, followed by a division of the security status evaluation level of the segment structure, as well as a construction of an unknown measurement function, with the weight determined by the G2 method based on entropy improvement, and the risk level determined based on the confidence recognition criterion. The model is applied to a metro shield tunnel in Hangzhou to evaluate the security status of its segment structure. The research results indicate that the application of uncertainty measurement theory can accurately evaluate the security level of tunnel segments, with accurate results and strong practicality.