By using the nonlinear polarization rotation, a thulium doped mode-locked multi wavelength fiber laser was achieved. In the ring cavity, a 1 565 nm fiber laser pumps a 3 m long thulium doped fiber. Filtering is realized by the nonlinear polarization rotation effect.When the pump power is 800mW, the pulse output of the passively mode locked state is realized by adjusting the fiber polarization controller. The pulse repetition frequency is 3.178 MHz and the pulse width is 617 ps.Further increasing the pump power, the laser is working at a multi wavelength state. By adjusting the fiber polarization controller, a stable 1~5 wavelength laser output is obtained at a room temperature, and the edge is less than 40～60 dB.