Abstract: As a direct excavation component of Full Face Rock Tunnel Boring Machine (TBM), the cutterhead bears the full load during the rock breaking. Its strength reliability is an important index for evaluating the performance of TBM cutterhead. Under the influence of complex geological conditions and the mechanism of cutter-rock interaction, the load borne on the cutterhead in the process of excavation is highly variable. Therefore, the strength performance of the cutterhead can meet the engineering requirements under a single specific working condition. To address this issue, we developed a systematic method for analyzing the strength reliability of the TBM cutterhead under random loads. Employing the cutterhead-rock interaction model, the rock breaking load of the cutterhead is obtained during the tunnelling process, which is then statistically analyzed to get its distribution characteristics and corresponding parameters. Subsequently, the random load is constructed based on the distribution parameters, and the strength reliability of the cutterhead is analyzed by Monte Carlo method. The results show that the rock-breaking loads on the two cutters situated at the outer edge are pivotal in determining the strength failure of cutterhead, accounting for up to 2/3 of the total weight. Moreover, high-speed construction in conventional rock formations or maintaining the normal excavation speed in hard-rock formations will significantly reduce the strength reliability of the cutterhead. These findings can provide a reference for the geological adaptive design of cutterhead and the control of TBM tunnelling parameters.