Abstract: As soft rock tunnels have the disadvantages of high construction risk and high complexity of support structure and construction process, it is difficult to directly calculate the limit state function of tunnel structure. So, this paper discusses an analysis method for the reliability of the tunnel system using finite element numerical simulation in combination with multiple response surface methodology and Monte Carlo method. Its suitability was verified in the case of one soft rock subway tunnel in Qingdao. The results showed that the surrounding rock characterized by "soft upper ground and hard lower ground" had a very large difference in lithology between the upper and lower parts, and the system failure probability of tunnel structure was mainly affected by the upper soft rock and rarely affected by the lower hard one; a change in the elastic modulus (E1) and internal friction angle (φ1) of pebble bed had the most significant impact on the system failure probability, and the tunnel system failure probability increased with the increasing of parameter variability of surrounding rock; due to the relevance between failure modes, it is not adequate only to take into consideration the failure of out-of-limit tunnel deformation or insufficient support bearing capacity, while the system reliability study based on multiple failure modes using deformation and bearing capacity as the controlling conditions was more suitable for the soft rock tunnel structure.