A kind of two-layer coated long period fiber grating sensor structure model is proposed based on fiber grating coupling theory.One layer is copper metal film plated on the outer cladding of fiber

another layer is sensitive film coated on the layer of copper film.Characteristics of the mode field and transmission of the two-layer coated long period fiber grating are analyzed and simulated.The influences of film parameters on the characteristics of the transmission are studied.The characteristics of refraction of sensitive film change with environmental and metal film is used

resonant wavelength is adjusted through temperature and strain.The results can provide theoretical basis for optimal design of high sensitivity long period fiber grating sensor.