To comprehensively and accurately evaluate the stability of a shield tunnel face under pore water pressure, a reliability analysis method for a double logarithmic spiral failure mechanism based on the limit analysis theorem and the random response surface theorem is proposed. The pore water pressure coefficient expresses the variation in pore pressure caused by groundwater, and the safety coefficient results obtained from the upperlimit analysis combined with the Latin hypercube sampling technique are used to establish the approximate limit state equation with Hermite polynomial expansion. Furthermore, the Monte Carlo simulation is used to obtain the failure probability characteristics of the tunnel face to verify the validity of the response surface method. The proposed method is used to analyze the influence of the variability of soil parameters, groundwater level, and support force on the failure probability of the tunnel face and applied to the reliability study of the tunnel face in the Xiangjiang tunnel. The results reveal that the proposed method can effectively evaluate the reliability of a tunnel face and provide a theoretical reference for selecting tunnel face support force in engineering.