The foundation of the middle pylon of Taizhou Bridge is located above the overlying deposit with the height of 200 m in the water. The round rectangular caisson foundation with the plane dimension of 58 m×44 m and the height of 76 m is employed. To verify the safety and stability of the middle pylon of Taizhou Bridge, a physics model with the scale of 1∶100 to the real structure is built up. The ultimate bearing capacity of the caisson foundation and the influence of sinking depth, soil moisture content, and the side wall friction on the bearing capacity are obtained.