The filtering characteristics of the fiber loop mirror filter, which is composed of multi-stage high birefringent fibers (HBF) is studied. The theoretic transfer function of the filter made of N-stage HBFs, and the expression are obtained when N is 1, 2 or 3; the polarization independence of the filter is analyzed, and the relation between the frequency response and the parameter of filter such as the length, beat length of HBFs and the angles between HBFs is studied; finally, some experiments are performed to check the theory, and the result shows to have good agreement with the theoretic result. The filter, which is based on N-stage HBFs loop mirror, has better stability than all-fiber Mach-Zehnder filter, is flexible in application, and has the advantages such as polarization independence, low insertion loss and low cost, so it has potential application in the fields of demodulation of fiber sensor, tunable filber laser and fiber filter of optic communcatiion.