A new structure optical wavelength-selective switch based on fiber loop mirror and fiber Bragg grating is studied. The dynamic range of greater than 17 dB and insertion loss of 0.5 dB at wavelength-selective port were obtained. The measured spectra and numerical simulation indicate that the imperfect of the device can be attributed to the definite difference between the two arms, which was about 1.35 mm. Devices with better characteristics can be developed by decreasing the difference.