The　pulse　compression　effects　of　passive　mode　locker,　such　as　graphene　and　Kerr　lens　medium,　which　has　been　inserted　into　a　synchronously-pumped　optical　parametric　oscillator　(SPOPO)　pumped　by　pulse　laser,　and　a　continuous-wave　(cw)　pumped　actively　mode-locked　OPO　has　been　studied　theoretically.　By　solving　the　nonlinear　coupled-wave　equations　in　the　plane-wave　approximation,　we　simulate　the　relations　of　the　pulse　width　and　peak　power　of　the　signal　pulses　to　the　normalized　aperture　radius,　the　nonlinear　crystal　length　and　the　beam　radius　on　the　nonlinear　crystal.　The　numerical　results　indicate　that　the　Kerr　lens　medium　and　graphene　are　both　favorable　for　the　pulse　compression　in　the　SPOPO,　and　each　of　them　has　different　advantages.　Whereas　in　the　actively　mode　locked　OPO,　the　Kerr　lens　medium　may　be　a　better　alternative　for　the　pulse　compression.　(C)　2015　Elsevier　GmbH.　All　rights　reserved.