An　average　power　of　58　W,　pulse　width　of　40　ps　at　1　KHz　repetition　rate　of　Nd:　YAG　picosecond　laser　is　reported.　It　used　an　etalon　to　directly　get　pulse　width　of　135　ps　from　Nd:　YVO4　mode　locked　laser　in　1064　nm,　which　repetition　rate　was　88　MHz.　When　the　seed　pulses　were　injected　into　the　double　length　of　regenerative　LD　side-pump　Nd:　YAG　cavity　at　1　KHz　repetition　rate,　the　single　pulse　energy　was　amplified　to　3　mJ,　the　pulse　width　was　compressed　to　99　ps,　beam　quality　of　M＜^＞2　factor　was　1.3.　The　single　pulse　energy　was　amplified　up　to　58　mJ,　the　pulse　width　was　self　compressed　to　40　ps,　beam　quality　of　M＜^＞2　factor　was　approximately　3.5　after　single　passing　three　stages　of　double　high　gain　LD　side-pump　Nd:　YAG　module.　Beam　pointing　was　about　40　urad.　The　stability　for　pulse　to　pulse　RMS　was　less　than　3%.　A　thin-film　polarizer　and　a　quarter-wave　plate　was　inserted　into　the　regenerative　amplification　cavity　to　let　pulses　double　travel　the　same　geometric　path　basis　on　pulse　polarization.　Serrated　aperture　were　used　in　the　amplification.　That＇s　beneficial　to　decrease　the　nonlinear　effect　for　the　high　power　in　the　crystal.　High　gain　LD　side-pump　Nd:　YAG　module　could　lead　the　pulse　energy　amplify　more　and　self　compress　the　pulse　width.　Double　length　of　regenerative　cavity　was　used　to　enhance　the　optical　cavity　length,　it　greatly　decreased　the　laser＇s　volume　and　improved　stability　of　picosecond　laser.　It＇s　a　nice　way　for　high　power　picosecond　laser　and　the　laser　system　would　be　more　simple　and　smaller.