Based　on　theoretical　calculation　of　the　stored　energy　and　small-signal　gain　coefficient　of　the　travelling　wave　amplifier,　the　characteristics　of　the　output　laser　were　simulated.　With　the　increment　of　the　pumping　current,　the　stored　energy　and　small　signal　gain　coefficient　increase　rapidly.　And　amplifier　energy　extraction　efficiency　can　reach　more　than　76%.　In　terms　of　the　output　energy,　it　rises　linearly　with　the　increasing　of　the　pumping　current.　When　the　pumping　current　is　80　A,　a　798　mJ　laser　pulse　can　be　obtained.　Related　experiment　is　carried　out　on　the　basis　of　theoretical　simulation.　In　this　experiment,　a　pulse　with　350　mJ　energy,　10　Hz　repetition　frequency,　10　ns　width　is　used　as　the　seed.　The　size　of　the　Nd:YAG　crystal　rod　in　amplifier　is　Φ7　mm×134　mm　and　the　doping　concentration　is　1.1　at%.　The　maximum　peak　power　of　laser　diode　(LD)　is　24　kW.　In　order　to　control　the　temperature　of　the　crystal　working　environment,　three　thermoelectric　coolers　are　chosen　with　a　maximum　power　of　66　W.　Ultimately,　a　700　mJ,　10　ns,　10　Hz　laser　pulse　is　obtained　for　single-pass　amplification.　The　beam　qualities　of　horizontal　and　vertical　direction　are　7.9　and　12.4,　respectively,　measured　by　the　beam　quality　diagnostic　instrument　M-200S.　©　2018,　Science　Press.　All　right　reserved.