In this paper a method using transfer matrix is introduced to calculate the spectra of fiber gratings.With this method the authors analyze the reflective spectra of FBG with different aperdization,phase-shift gratings and sampled gratings,and also dispersion specialty of chirped grating.The effects of grating parameters on the grating specialties were observed.In the end we testified the theory analysis on aperdized gratings and sampled gratings by experiments.