In　this　paper,　we　report　a　simpler　and　efficient　hybrid　laser　amplification　system,　which　delivers　a　single　pulse　energy　of　20　mJ　at　500　Hz　with　a　pulse　width　of　278　ps.　This　hybrid　amplification　system　mainly　consists　of　a　hundred-picosecond　all-fiber　structure　seeder,　a　regenerative　amplifier　and　a　single-pass　amplifier.　The　hundred-picosecond　laser　pulse　from　the　fiber　seed　is　first　amplified　to　4　mJ　by　a　regeneration　amplifier　with　a　normally　doped　Nd:YAG　rod.　For　the　improvement　of　the　laser　energy,　the　QCW　side-pumped　Nd:YAG　single-pass　amplifier　has　been　adopted　at　the　second　stage　of　solid-state　amplifiers.　To　reduce　the　serious　thermal　effect,　the　bonded　composite　YAG-Nd:YAG-YAG　rod　crystal　is　used　as　the　gain　medium,　which　possesses　6　mm　in　diameter　and　85　mm　in　effective　pumped　length,　and　a　doping　concentration　of　0.8%.　Finally,　20　mJ　output　energy　and　278　ps　pulse　duration　are　obtained　with　a　peak　power　of　72　MW,　and　its　beam　quality　factor　is　1.7.　In　addition,　this　laser　amplifier　is　confirmed　by　latter　theoretical　simulations　of　laser-induced　plasma　in　silicon-based　photodiode.　The　high-energy　amplification　of　the　hundred-picosecond　pulse　is　realized　in　this　hybrid　amplifier　system,　which　will　be　used　as　laser　irradiation　source　in　laser-induced　damage　application.