Mid-infrared　tunable　femtosecond　fiber　laser　has　attracted　many　attentions　for　widely　applications.　Recently,　Raman　soliton　self-frequency　shifting　effect　in　nonlinear　fibers　was　regarded　as　a　promising　approach　to　obtain　such　pulse　laser.　However,　other　higher　order　nonlinear　effects　occurred　in　fibers　will　limit　the　pulse　energy　promoting.　So,　to　further　enhance　the　pulse　energy　of　Raman　soliton,　we　proposed　a　novel　method　where　the　rare-earth　doped　nonlinear　fiber　was　used　as　nonlinear　medium.　We　numerically　investigated　the　impacts　of　the　optical　gain　on　the　pulse　energy,　pulse　width　and　spectrum　of　the　wavelength　shifting　Raman　soliton.　The　results　show　that　as　the　Raman　soliton　shifted　into　the　wavelength　range　where　the　optical　gain　introduced,　the　pulse　energy　of　the　soliton　pulse　was　enlarged　by　several　times,　and　the　pulse　width　was　compressed　to　45　fs.　Meanwhile,　the　wavelength　of　the　femtosecond　Raman　soliton　pulse　can　be　widely　tuned　by　changing　the　optical　net　gain.　Therefore,　by　using　rare-earth　doped　fiber　as　the　nonlinear　medium　and　gain　medium,　we　can　achieve　the　generation　of　mid-infrared　tunable　high　pulse　energy　femtosecond　pulse　laser.　©　2020,　Science　Press.　All　right　reserved.