A　high　pulse　energy　Yb-doped　all-fiber　dual-cavity　laser　oscillator　is　reported,　based　on　the　pulse　generation　mechanism　of　passive　Q-switch　with　large　core　fiber　saturable　absorber.　Sequential　pulses　with　49-ns　pulse　duration　and　21-W　average　power　operating　at　1080　nm　can　be　achieved　in　the　scheme　using　the　Yb-doped　fiber　with　the　core-diameter　of　10　mu　m.　The　repetition　rate　varies　from　similar　to　1　to　113.6　kHz,　while　the　incident　pump　power　increases.　The　monolithic　all-fiber　dual-cavity　oscillator　can　achieve　the　highest　pulse　energy　of　187　mu　J.　Moreover,　using　the　all-fiber　scheme　with　the　core-diameter　of　uniform　20　mu　m,　the　single-pulse　energy　can　be　further　scaled　up　to　484　mu　J,　which　is　directly　the　output　from　the　all-fiber　oscillator　without　additional　amplifiers.