Study　of　the　damage　characteristics　of　silicon-based　photodetectors　is　of　great　significance　in　improving　application　performance,　but　few　studies　of　laser-induced　damage　have　been　undertaken　on　photodetectors　irradiated　by　hundred-ps　fiber　lasers.　In　this　work,　we　demonstrate　an　all-fiber　ps-pulsed　laser　system　which　outputs　a　pulse　width　of　226.5　ps　and　an　average　power　of　20　W　at　2.4　MHz　repetition　rate,　with　high　beam　quality　and　pulse　stability.　Experiments　use　this　fiber　amplifier　to　irradiate　a　silicon-based　positive-intrinsic-negative　(PIN)　photodiode.　The　changes　in　detector　performance　and　surface　morphology　are　confirmed　by　systematic　experiments　on　the　laser-irradiated　detector.　The　results　show　that　detection　performance　was　sensitive　to　laser　energy,　and　the　failure　damage　threshold　was　about　864　kW　cm(-2).　Based　on　hydrodynamics　theory,　we　simulated　the　laser-induced　plasma　density　distribution　in　a　PIN　photodiode　and　studied　the　thermal　and　plasma　damage　mechanisms　in　the　PIN　photodiode.