High-power　ultrafast　fiber　lasers　are　important　sources　for　a　number　of　applications　including　material　processing,　pump　source　for　optical　parametric　oscillator,　and　supercontinuum　generation.　Ultrafast　thulium-doped　fiber　lasers,　which　extend　the　wavelength　range　of　fiber　lasers　from　1.8　to　2.1　mu　m,　have　rapidly　developed　in　the　last　several　years　and　the　average　output　power　of　the　ultrafast　thulium-doped　fiber　amplifiers　has　reached　a　hundredwatt　level.　The　broad　and　smooth　gain　spectrum　of　thulium-doped　fiber　makes　it　a　well-suited　gain　medium　for　generating　the　ultrashort　laser　pulses　and　broad　wavelength　tunability.　However,　previous　reports　on　ultrafast　thulium-doped　fiber　lasers　and　amplifiers　were　related　to　non-PM　fiber　configuration.　These　ultrafast　thulium-doped　fiber　lasers　and　amplifiers　may　suffer　the　environmental　instability,　which　means　that　these　fiber　sources　are　sensitive　to　externally-induced　changes,　like　significant　temperature　variations　and　mechanical　perturbations　which　will　influence　the　fiber　birefringence　property.　An　effective　method　to　eliminate　this　environmental　instability　is　to　build　an　all-PM,　thulium-doped　all-fiber　MOPA　configuration　where　the　light　polarizes　only　along　the　slow　or　fast　axis　in　the　PM　fiber　and　PM-fiber　components.　Here,　we　demonstrate　a　high-power　all-polarization-maintaining　picosecond　thulium-doped　all-fiber　master-oscillator　power-amplifier　(　MOPA)　system.　The　linearly-polarized　thulium-doped　all-fiber　MOPA　yields　203　W　of　average　output　power　at　central　wavelength　of　1985　nm　with　a　polarization　extinction　ratio　of　＞15　dB.　The　pulse　duration　of　15　ps　at　611.5　MHz　repetition-rate　results　in　a　peak-power　of　22　kW　in　the　final　thulium-doped　fiber　power　amplifier.　To　the　best　of　our　knowledge,　this　is　the　highest　average　output　power　ever　reported　for　a　picosecond-pulsed　thulium-doped　all-fiber　laser　at　2　mu　m　wavelength.　Furthermore,　high-power　linearly-polarized　thulium-doped　fiber　laser　with　compact　and　simple　design　is　greatly　demanded　for　a　variety　of　applications,　such　as　coherent　polarization　beam　combination,　and　frequency　conversion　in　nonlinear　crystals.