[en] The analysis of contact problem in multiple wall piping system is especially necessary for the double wall pipings of high temperature gas-cooled reactors, in which the spacers may contact to the internal surface of pipes, prevent thermal expansion and raise stress, and complicate the behavior of piping system by the change of contact state. A new analytical method for the contact problem in double wall piping system is presented, looking back to Herz's equation, considering many additional restraint conditions and using the special contact model. This new analytical method is the Newton-Raphson method which has comparatively simple algorism and good convergence. Four example calculations using this new analytical method are shown, and evaluated. Finally, several problematical points are explained. (Nakai, Y.)