A kind of Photonic Crystal Fiber based Long Periond Grating (PCF-LPG) was analyzed on basis of the local coupled-mode theory.Transmission spectrum of the coupling between LP01and LP02,LP01and LP11,was numerically modeled after building the collapse model.Compared with transmission spectrum calculated with the coupled mode theory,the local coupled-mode theory was found in a good agreement to analyze the strong PCF-LPGs.The changes of resonant wavelength were discussed in different grating periods,number of periods and the depths of cladding collapse.The results indicate that,with the increase of grating period,the resonance wavelength shifts to shorter wavelength;with the increase of number of periods,the resonance depth increases;with the increase of depths of cladding,the resonance wavelength shifts to longer wavelength.