A passive mode-locked fiber laser based on nonlinear polarization rota tion(NPR) effect was reported and demonstrated,the pump source of this cavity is 980nm diode and the gain medium is a 5m long erbium-doped fiber.Two polari za tion controllers(PC1and PC2) combine with a polarization dependent isolator(P DI) were used to generate NPR effect,as the equivalent saturable absorber,gene rate stable mode-locked pulse output with the pulse width is 36.02ns.And the i n fluences of different cavity length on laser’s output were investigated,the th reshold value of pump power will decrease with the increase of the length of the cavity.The laser combine with a Sagnac ring,which was consist of a 3dB couple r,a 1m polarization-maintain-fiber(PMF) and a PC,used as a comb filter.Throu gh experiments,tunable multi-wavelength output from single to five wavelengths in C-band is realized.The long-term stability of the output spectrum was also t ested,the output spectrum of the laser shows little change at room temperature, so it exhibits excellent stability.The results show that the laser could gener ate mode-locked pulses and tunable multi-wavelength.The laser will have broad a pplication prospect and high research value,such as biomedical field and wavele ngth multiplexing system.