Based on an erbium-doped double pass backward (DPB) superfluorescent fiber source (SFS), by employing a improved Mach-zehnder interferometer filter (MZI) as spectrum slicing and spectrum pre-slicing component, respectively, two multi-wavelength superfluorescent fiber sources (MW SFSs) with channel spacing of ～0.8 nm are got. For the 20 channels around 1550 nm (from 1542 to 1559 nm), the power fluctuations are less than 0.5 dB. The extinction of the former is as high as 27 dB, and the latter is ～18dB. With the latter schematic, output power as high as 25.3 mW with pump efficiency of 34.8% is achieved under a limited 980 nm pump power of 72.8 mW. By changing the difference of the arms of the Mach-Zehnder interferometer filter, 50 channels around 1550 nm with spacing of ～0.4 nm are got, and the extinction is ～16 dB.