The paper proves sufficiently and technically structural reliability of the formwork with H-shaped Steel truss applied to the outside walls in the reinforced concrete box culvert.It also makes some static analyses through structural finite element method.Calculation indicates that structural bearing capacity and stiffness of the formwork can meet national standard requirement.In the construction process of the formwork applied to the tunnel with cross-section of box-culvert under Lake Qinshan,The monitoring results of lateral deformation of the formwork are smaller than theoretical calculations,which shows the designing scheme of the formwork applied to construction of the tunnel is feasible completely.