The surface of poly(ethylene naphthalate) film applicable to high temerature insulator for convection microwave oven was modified with silicone coating solutions in the presence of silane crosslinking agent. The structure and properties of the PEN films were investigated by using Fourier transform IR spectroscopy, viscometry, microscopy, and tensile tests. The experimental results showed that the coating with silicone enhanced thermal stability up to $200^{circ}C$, and slightly lowered the tensile strength and elongation of the PEN films. Judging from dimensional stability results the silicone coated PEN films can not be used for higher temperature insulator above $230^{circ}C$. Serious dimensional contraction of films was obtained during heat treatment at $250^{circ}C$ even for 1h. However, the surface of those films still have same chemical structure of silicones. Therefore, If we use PEN film prestretched at $230^{circ}C$ as base one it will be possible to prepare a high temperature insulator up to $230^{circ}C$. Conclusively, a silicone coated PEN film can be suitable for the application to convection microwave oven door insulator at high temperature up to $230^{circ}C$.