In the process of shield tunneling, the abnormal increase of cutterhead temperature will lead to the increase of cutterhead wear and even cutterhead deformation, which would seriously affects shield tunneling and construction safety. In order to realize real-time monitoring of cutterhead temperature and avoid the harm caused by overlarge cutterhead temperature, an online cutterhead temperature monitoring system for large-diameter slurry shield used in Wangjiang Road River-crossing Tunnel Project in Hangzhou is established. The monitoring system, combined with wireless transmission technology, uses sensors installed on the back of the cutterhead to collect temperature data, and organizes and analyzes the data. The results show that: (1) The system can avoid the interference of signal shielding and slurry shield tunneling, and monitor the cutterhead temperature stably for a long time. (2) In a single tunneling ring, the cutterhead temperature changes periodically and matches with the working flow of shield tunneling. (3) During continuous tunneling, the heat generated by tunneling will accumulate steadily on the cutterhead, which makes the peak value of cutterhead temperature curve continuously increase. (4) When the temperature of the cutterhead is abnormally increased, by injecting a dispersant into the cutterhead and observing the temperature change of the cutterhead, the conditions such as the mud cake on cutterhead and the geological mutation in front of cutterhead can be distinguished. The online monitoring system of cutterhead temperature mentioned-above can be used to analyze cutterhead conditions, judge geological changes and adjust driving parameters.