Mode-locked Yb-dpoed fiber laser has very important application in laser micro-processing industry.The multi-wavelength mode-locking phenomenon in an all-fiber ring-cavity Yb-doped fiber laser is demonstrated in this paper.Without any fr equency-select component or conventional saturable absorber in the cavity,only by the inhomogeneous broa dening effect of Yb-doped fiber and the equivalent saturable absorption of the non-pumping part of the gain fiber,stable multi-wavelength mode-locking pulses are achieved.Related analysis is made.W hen the pumping power reaches 128mW,the mode-locking occurs.The output power is 1.5mW and th e repetition rate is 14.85MHz,which is corresponding to the fundamental frequency of the cavity.Th e pulse signal-to-noise ratio is 60dB.Increasing the incident pumping power,stable mode-locking puls es are still obtained and multiple peaks appear in their spectra.The central wavelength locates aro und 1035nm and the average wavelength spacing is about 1.5nm.The number of peaks and their spacing can be changed by adjusting the polarization controller (PC).When the incident pumping power is increased to the maximum of 330mW,the average output power is measured to be about 7.23mW with 6equally spaced wavelength peaks.