The　pulse　properties　of　continuous　wave　(CW)　pumped　mode-locked　singly　resonant　optical　parametric　oscillator　(OPO)　by　acousto-optic　modulation　(AOM)　mode-locking　are　studied　theoretically.　The　influences　of　pump　intensity,　transmittance　of　output　coupler,　parameters　of　acousto-optic　modulator　on　pulse　properties　are　investigated　numerically.　It　can　be　seen　that　lower　pump　power　and　higher　transmittance　will　be　favourable　for　pulse　compression　in　the　condition　that　the　pump　power　is　large　than　the　threshold.　Additionally,　deeper　modulation　depth　and　higher　modulation　frequency　of　active　modulator　will　also　be　helpful　for　pulse　compression,　whereas　the　pulse　energy　will　be　suppressed.