NOVELTY - An interphotonic crystal fiber optical interference methane sensing device comprises broadband light source, optical circulator, optical fiber methane sensor, test chamber, switch valves, mass flow controllers, spectrum analyzer and computer, where the light source is connected to optical fiber methane sensors, the optical fiber methane gas sensor is located in test chamber, the test chamber is passed into test methane gas inlet and outlet, the valve is connected to mass flow controllers, the optical fiber methane sensor comprises single-mode fiber, photonic crystal fiber and two welded areas.    USE - Interphotonic crystal fiber optical interference methane sensing device.    ADVANTAGE - The device has high sensitivity, good stability and good selectivity.    DETAILED DESCRIPTION - An interphotonic crystal fiber optical interference methane sensing device comprises broadband light source, optical circulator, optical fiber methane sensor, test chamber, switch valves, mass flow controllers, spectrum analyzer and computer, where the broadband light source is connected to the optical fiber methane sensors through the input end of the optical circulator having single-mode optical fiber, the optical fiber methane sensor reflected interference signal is returned to the single-mode optical fiber and connected by an optical spectrum analyzer and meter at the output of computer, the optical fiber methane gas sensor is located in the test chamber, the test chamber is passed into the test methane gas inlet and outlet, the switching valve is connected to mass flow controllers for measuring methane gas, the optical fiber methane sensor comprises single-mode fiber, photonic crystal fiber and two welded areas for single-mode solid-core photonic crystal fiber, the inner wall of photonic crystal fiber cladding air holes are coated with polymer sensitive film, the polymer sensitive film comprises polymer cage molecules E-(OC2H5)6 methane sensitive polycarbonate resin film having thickness of 200-300 nm, the polymer cage molecules E-(OC2H5)6 methane sensitive polycarbonate resin film comprises polycarbonate resin, the polymer cage molecules E-(OC2H5)6 methane sensitive polycarbonate resin film is prepared by dissolving polymer cage molecules in tetrahydrofuran, mixing and coating in the inner wall of photonic crystal fiber cladding air holes by using pneumatic driving unit.