Based on a semiconductor optical amplifier and sampled fiber Bragg gratings, polarization-controlled waveband switching in multiwavelength fiber laser is successfully demonstrated at room temperature by using high polarization selectivity of a polarization beam splitter. A multiwavelength-switching operation between eight and six laser lines with signal to noise ratio over 35 dB and wavelength spacing of ${sim}0.8nm$ has been successfully demonstrated. The switching displacement of the proposed laser was ${sim}7.1nm$. The intensity unevenness between different laser lines was measured to be less than 6.5 dB. The switching displacement between wavebands (groups of contiguous wavelengths), wavelength channels, and their spacings can be flexibly designed by the selected comb filters.