Microstructure　evolution　characteristics　of　a　powder　metallurgy　(PM)　Ni-based　superalloy　during　hot　deformation　were　investigated　by　isothermal　compression　tests　at　1050　&　ring;C-1200　&　ring;C　for　strain　rates　of　0.001　s-　1-1　s-　1　in　this　work.　And　the　relationships　between　the　dynamic　recrystallization　(DRX)　behavior,　DRX　mechanisms,　twins,　and　gamma　were　discussed.　The　results　showed　that　discontinuous　dynamic　recrystallization　(DDRX)　which　was　nucleated　by　grain　boundary　bulging,　occurred　in　all　deformation　parameters　in　this　superalloy.　For　gamma/gammapoly-　phase　region　deformation　(1050　&　ring;C-1140　&　ring;C),　the　volume　fraction　of　dynamically　recrystallized　(DRXed)　grains　increased　with　the　increase　in　strain　rates.　The　finding　suggested　that　gamma　particles　promoted　the　nucleation　of　subgrains　in　deformed　grains,　causing　the　continuous　dynamic　recrystallization　(CDRX)　mechanism,　characterized　by　subgrain　continuous　rotation,　to　be　another　dominant　DRX　mechanism　except　for　DDRX.　Moreover,　the　formation　of　twin　boundaries　occurred　under　the　comprehensive　control　of　DRX　and　grain　boundary　migration.　DRX　promoted　the　formation　of　twin　boundaries,　but　at　high　temperatures,　the　reduction　of　the　free　energy　from　grain　growth　was　higher　than　twin　formation,　causing　the　possibility　of　twin　formation　to　be　reduced.　For　gamma/gamma　poly　-phase　deformation,　the　area　fraction　and　size　of　gammaincreased　with　decreasing　compression　temperatures　and　increasing　strain　rates,　and　high　compression　temperatures　and　low　strain　rates　promoted　the　further　dissolution　of　gamma.　The　optimum　hot　deformation　processing　conditions　for　PM　Ni-based　superalloy　is　1110-1140　&　ring;C/　0.01-0.1　s-1.