The　single-walled　carbon　nanotubes　(SWCNT)　could　be　used　as　saturable　absorber　in　Q-Switched　and　mode-locked　lasers.　In　this　paper,　the　influence　of　the　concentration　and　the　ultrasound　time　on　the　absorption　coefficient　of　the　single-walled　carbon　nanotubes　was　discussed.　The　structure　and　morphology　of　the　single-walled　carbon　nanotubes　were　investigated　by　the　atomic　force　microscope(AFM)　and　the　scanning　electron　microscopy(SEM).　When　the　single-walled　carbon　nanotube　saturable　absorbers　(SWCNT-SAs)　were　used　in　both　the　Yb-doped　double　cladding　fiber　laser　and　the　solid　state　lasers,　the　Q-switched　pulses　were　obtained.　And　we　use　the　single-walled　carbon　nanotubes　saturable　absorber　(SWCNTs)　in　the　passively　Q-switched　Nd:YCOB　(Nd3+:(Nd3+:YCa4O(BO3)(3))　laser,　a　duration　of　1.6　mu　s　pulses　were　obtained　at　the　center　wavelength　of　1085.3　nm,　a　175　mW　output　power　were　obtained　at　the　pump　power　of　9W.