A type of insulator-metal-insulator surface plasma polariton interface is proposed. According to Maxwell equations and boundary conditions, the dispersion characteristics of metal surface are analyzed. Finite-difference-time-domain (FDTD) method is used to simulate the field enhancement effect of Bow-tie and rectangular nano-structure under a single light source radiation and the field enhancement effects of double Bow-tie nano-structure under single and double light sources radiation respectively. Comparing and analyzing the simulation results show that the point effect plays an important role in the field enhancement effect of plasma polariton, and the field enhancement effect is associated with the distance between the nano-structures. Only when the distance between the nanostructures is right, the maximum field enhancement can be obtained.