We　report　high-energy,　high-efficiency　second　harmonic　generation　in　a　near-infrared　all-solid-state　burst-mode　picosecond　laser　at　a　repetition　rate　of　1　kHz　with　four　pulses　per　burst　using　a　type-I　noncritical　phase-matching　lithium　triborate　crystal.　The　pulses　in　each　burst　have　the　same　time　delay　(similar　to　1　ns),　the　same　pulse　duration　(similar　to　100　ps)　and　different　relative　amplitudes　that　can　be　adjusted　separately.　A　mode-locked　beam　from　a　semiconductor　saturable　absorber　mirror　is　pulse-stretched,　split　into　seed　pulses　and　injected　into　a　Nd:YAG　regenerative　amplifier.　After　the　beam　is　reshaped　by　aspheric　lenses,　a　two-stage　master　oscillator　power　amplifier　and　4f　imaging　systems　are　applied　to　obtain　a　high　power　of　similar　to　100　W.　The　532　nm　green　laser　has　a　maximum　conversion　efficiency　of　68%,　an　average　power　of　up　to　50　W　and　a　beam　quality　factor　M-2　of　3.5.