Abstract: To explore new structures of comb filters, a new Sagnac loop filter based on the sampled fiber Bragg grating was proposed. Using the theory of Jones matrix, the theoretical model of filter was established. Theoretical analysis and numerical simulation of transmission spectra of the proposed filter were carried on. By choosing the different value of the sampled fiber Bragg grating length L, optical fiber ring arm length difference L, and the sampling period P, six kinds of narrow-band comb transmission spectrums with discrete spectral lines, high reflectivity, and equal interval can be obtained. The spectrums have good wavelength selectivity and good channel isolation. The simulation results show that this filter can be used in the multi-channel narrow band filter of the wavelength division multiplexing system, dual-wavelengthfiber laser, and the distributed sensing system, etc. It provides a certain reference for the filter combining fiber Bragg grating with the structure of the Sagnac loop in research and application.