A new index called global sensitivity index by global sensitivity analysis was proposed to evaluate the relationship between tunnel structure health monitoring data and tunnel health status. Global sensitivity analysis could quantitatively and systematically evaluate the parameter sensitivities and their variations under various conditions, resulting in an improved understanding of relationships between monitoring data and tunnel health status, and suggesting potential approaches to the improvement of tunnel health evaluation model. Moreover, a case study of global sensitivity analysis was presented to evaluate the monitoring data on Wuhan Yangtze River Tunnel. The achievement of this global sensitivity analysis leads to the parameter sensitivities had been quantified, and the sensitive and insensitive parameters were distinguished. The sensitive parameters could then be identified as major factors for monitoring or administrative maintenance. The variations in parameter sensitivity index associated with various target functions, parameter ranges and distribution were examined. The variations of parameter sensitivities were observed with various conditions, suggesting that sensitive and insensitive parameters maybe inversed under different conditions.