Random　Decrement　Technique　(RDT)　is　a　widely　used　method　to　extract　free　decay　response　data　by　averaging　time　segments　obtained　under　certain　triggering　condition　from　structural　vibration　response.　And　thus,　different　triggering　condition　will　inevitably　lead　to　different　Random　Decrement　Signature　(RDS)　and　different　modal　parameters.　The　quality　of　RDS　has　significant　influence　on　the　modal　parameter　identification　results.　Based　on　three　assessments　criteria　for　RDS＇s　quality,　statistical　analysis　of　change　law　of　RDS　with　different　triggering　level　and　length　of　time　history　are　carried　out　by　a　SDOF　system　and　a　6-DOF　system.　A　multi-triggering　method　is　proposed,　by　which　a　better　RDS　can　be　obtained.　Numerical　simulation　and　the　practical　engineering　application　verified　the　recommended　method　and　values.