The evaluation of the health state of an immersed tunnel is inevitably affected by the variety of influencing factors, the complex relationship between influencing factors and fuzzy characteristics of health evaluation criteria. A targeted method for analysis of the health conditions of an immersed tunnel in operation period is immature. As a case study of the health monitoring of the largest inland river immersed tunnel-Nanchang Honggu Tunnel, a fuzzy analytic hierarchy process (Fuzzy-AHP) method was carried out in this study, which merged different types of data from multiple sensors to map them into comprehensive evaluation value of the immersed tunnel. The hierarchical structure of the health evaluation index was established, and the layout scheme of monitoring sensors was designed through a comprehensive analysis of influencing factors. Additionally, the entropy weight method was introduced to modify the subjective characteristic of index weight in the fuzzy analytic hierarchy model, and then a Fuzzy-AHP evaluation procedure was built. Finally, the proposed evaluation model and evaluation procedure of immersed tunnel health states were verified by the field monitoring data of the Nanchang Honggu Tunnel. The comprehensive evaluation value V F was compared with the rating scales and countermeasures proposed in this study to determine the tunnel health state and corresponding countermeasures. The results indicate that the evaluation health of the whole tunnel sections of Nanchang Honggu Tunnel in December 2018 was in grade A, and further monitoring was needed. The V F values of sections located at the middle of the river and the final joint were slightly smaller than other sections. The proposed Fuzzy-AHP method can give a feasible and effective evaluation for immersed tunnel health states.