By　studying　PCY14-1B　type　axial　piston　pump　with　constant　pressure,　the　mathematical　model　and　formulae　for　calculating　the　important　parameters　are　given,　and　the　system　block　diagram　is　set.　The　dynamic　simulation　of　the　transfer　function　around　open　loop　is　accomplished　by　programming　based　on　Matlab.　Results　demonstrate　that　the　bigger　the　one-step　turning　frequency　w(r)　value　is　or　the　smaller　er　the　open　gain　coefficient　is,　the　more　stable　the　system　will　be.　After　showing　the　curves　under　dynamic　simulation,　the　corresponding　designing　principles　can　be　easily　proposed.