A tunable multi-wavelength erbium-doped fiber (EDF) laser based on nonlinear polarization rotation (NPR) is realized. A polarization-dependent isolator and a polarization-maintained fiber (PMF) are used as key elements of the laser. Both effects of self filtering and peak clamping generated from NPR, effectively alleviating the mode competition resulted from the homogeneous broaden of the EDF, ensure stable multi-wavelength operation at room temperature. The dispersive property of the cavity loss allows the lasing wavelength to be tuned within a range of 5 nm. Wavelength spacing can also be tuned by changing the effective length of PMFs, the period of the self filtering is determined by the birefringence of the cavity. Stable multi-wavelength operation with wavelength spacing of 0.25 nm and 0.75 nm is obtained as two pieces of PMFs and a polarization controller are combined into the cavity.