We　demonstrate　the　mode-locking　operation　in　an　all-polarization-maintaining　(all-PM)　erbium-doped　fiber　laser　by　exploiting　graphene　oxide　saturable　absorber　for　the　first　time.　The　self-started,　environmentally　stable　laser　directly　generates　linearly　polarized　soliton　pulses　of　502　fs　duration　at　a　repetition　rate　of　48.2　MHz　with　an　extinction　ratio　of　21.3　dB.　The　optical　spectrum　centered　at　1555.92　nm　has　3-dB　bandwidth　of　6　nm.　This　unique　combination　of　the　all-PM　configuration　and　the　novel　graphene　oxide　saturable　absorber　offers　an　ideal　approach　to　fabricate　a　compact　single-polarization　femtosecond　source　with　high　environmental　stability.