Tunable fiber lasers are widely applied in fiber communication, optical fiber sensing, laser spectroscopy, precision measurement and laser processing etc. Considering of the deficiencies of current tunable lasers in tuning, flexibility, stability and multi-wavelength power equalization, a novel C-band tunable multi-channel fiber laser based on a digital micromirror device (DMD) is proposed. This tunable laser uses erbium-doped fibers as the laser gain medium and an opto-DMD processor as a tuner to dynamically select arbitrary lasing wavelength. The laser has three tunable output channels in 1530~1560 nm with resolution of 0.055 nm/pixel, and each channel can be controlled independently. The side mode suppression ratio of laser signals is greater than 55 dB. The maximum laser output power is about 10 mW and the fluctuation of the center wavelength within 2 h is below 0.02 nm.