“LesnayaMuzhestvo Square” running tunnel on Line 1 of Saint Petersburg Metro went across the ancient river channel of the Neva River. A series of accidents occurred during the construction period and after the tunnel was put into use in 1975. In the late period, lots of water inflow with quicksand came into the tunnel, which resulted in surface settlement, deformation of the tunnel, serious damage of the structure and the close of the tunnel in 1995. After an introduction to the construction method, the course of the accidents and the countermeasures taken, the causes for the accidents are analyzed in the paper.