Multi-wavelength erbium-doped fiber laser based on twin-core fiber filter and nonlinear polarization rotation at room temperature is proposed. The compact in-fiber Mach-Zehnder comb-filter is formed by splicing a section of twin-core fiber (TCF) with two single mode fibers (SMFs). Due to the nonlinear polarization rotation (NPR) effect in the laser cavity, the laser can be made to operate in stable multi-wavelength lasing states by adjusting the states of the polarization controller (PC) appropriately. The wavelength shift is less than 0.02 nm, and the power amplitude variation is less than 0.4 dB, which shows the fiber laser has a good stability.