Birefringence fiber loop mirror has filtering characteristics. By cascading two loops, the transmission performance can be improved and become more flexible compared with that of the single-stage one. Such a simple cascading scheme which can improve filtering characteristics of loop mirror, is proposed. The transmission characteristics of the loop mirror filter constituted by birefringence fiber and Sagnac loop have been analyzed in detail. The filtering characteristics of two cascaded birefringence fiber loop mirror are discussed. By numerical simulation, explicit expression of the transmission spectrum for the cascaded mirrors with the high-birefringence fiber (HBF) length ratio of 1∶2 is obtained. Compared with its single-stage counterpart, the 3 dB bandwidth of the two-stage filter is compressed to approximately 7 nm and its quality factor reaches about 4.5. Experimental results conform well with the theoretical calculation, thus proving the validity of this theory.