We　report　a　high-energy,　high-average　power　burst-mode　picosecond　laser　system,　which　is　designed　for　space　debris　laser　ranging.　Pulses　from　a　Nd　:　YVO4　mode-locked　oscillator　are　first　stretched　by　a　piece　of　volume　Bragg　gratings　(VBG)　and　then　pass　through　an　improved　Michelson　interferometer　splitting　system　to　obtain　burst-mode　pulses,　which　the　relative　amplitude　and　time-delay　interval　of　each　4-pulse　in　bursts　can　be　adjusted　and　controlled.　A　regenerative　amplifier　(RA),　as　a　pre-amplifier,　is　adopted　to　decrease　the　repetition　frequency　of　the　seed　beam　from　80MHz　to　1　KHz　and　raises　the　energy　to　millijoule-level.　In　order　to　reduce　the　performance　requirement　of　the　damage　threshold　of　subsequent　optical　components　and　maximize　the　extraction　of　pulse　energy,　the　Gaussian　output　beam　of　the　RA　is　converted　into　a　ring　shaped　pattern　beam　using　an　aspheric　lenses　reshaping　system　with　the　conversion　efficiency　of　93%.　After　a　two-stage　master　oscillator　power　amplifier　with　4f　imaging　systems,　the　pulse　envelope　energy　is　up　to　100　mJ　with　the　pulse　duration　of　similar　to　100　ps.　To　obtain　high　power　green　light,　we　compared　the　conversion　efficiency　of　three　crystals.　When　the　fundamental　frequency　power　is　80W,　the　second　harmonic　conversion　efficiency　of　the　first　crystal　(LBO,　6x6x10,　theta=90　degrees,　Phi=11.4　degrees)　is　only　about　50%,　as　well　as　the　second　(GTR-KTP,　7x7x7,　theta=90　degrees,　Phi=23.5　degrees).　But　the　conversion　efficiency　of　the　last　crystal　(LBO,　6x6x15,　theta=90　degrees,　Phi=0　degrees),　reaches　68%　and　the　output　power　of　532　nm　as　high　as　50　W　is　obtained.