A novel method of risk analysis for the big or small shield tunneling projects was brought forward and validated. Firstly, the risk factors in big or small shield tunneling projects were systematically analyzed. Secondly, with a real big or small shield tunneling project as the example, the reliability method was brought forward to analyze the risk degree. Finally, the feasibility of this method was validated by comparing the obtained results with the progress of the project. The application of the reliability method is meaningful in reducing the risk degree of big or small shield tunneling projects by taking effective measures in advance.