Seawater　axial　piston　pump　is　a　critical　power　component　in　seawater　fluid　power　system.　As　the　properties　of　high　bulk　modulus　and　low　viscosity　of　seawater,　the　pressure　and　vibration　characteristics　of　the　seawater　axial　piston　pump　will　be　getting　poorer　than　the　traditional　oil　pump.　In　this　study,　the　pressure,　flow,　and　vibration　characteristics　for　a　seawater　axial　piston　pump　are　investigated.　The　three-dimensional　computational　fluid　dynamics　simulations　for　the　port　plate　with　non-grooved,　U-shaped,　and　triangle-based　pyramid　silencing　groove　designs　have　been　conducted　over　a　range　of　operating　conditions,　which　consider　the　fluid　compressibility　effect　and　cavitation　damage.　Measurements　of　pressure　ripple　and　pump　vibration　are　carried　out　at　various　loading　conditions　to　verify　the　results　of　simulation.　The　experiment　turned　out　that　the　well-designed　port　plate　can　mitigate　both　pressure　ripples　as　well　as　vibrations　of　the　pump.　This　research　will　lay　the　foundation　for　the　further　development　of　a　low　fluid　noise　seawater　axial　piston　pump.