The　forces　acting　on　the　actuator　used　in　a　reciprocating　capacity　control　system　are　analyzed　in　this　article.　The　dynamic　response　of　this　system　is　influenced　significantly　by　hydraulic　pressure　and　reset　spring　force.　The　performance　of　dynamic　response　is　tested　under　different　hydraulic　pressures　and　reset　springs.　The　results　show　that　the　influence　of　reset　spring　force　on　the　downward　speed　and　displacement　of　actuator　is　more　inconspicuous　than　the　hydraulic　pressure,　but　the　reset　speeds　decrease　obviously　when　the　reset　spring　force　is　small　(SPR2　and　SPR3).　The　maximum　downward　displacement　decreases　and　the　consuming　time　increases　with　the　decrease　in　the　hydraulic　pressure.　The　maximum　downward　speed　of　actuator　decreases　with　the　decrease　in　hydraulic　pressure　which　influences　the　reliability　and　life　of　this　system.　Therefore,　the　performance　of　dynamic　response　and　operating　lifetime　needs　to　be　considered　simultaneously　during　the　design　of　partial　stroke　press-off　inlet　valve　capacity　control　systems.