Single　cylinder　and　multi-cylinder　models　for　electron-controlled　assembly　pump　(ECAP)　were　established　in　AMESim　environment.　Through　numerical　simulation　and　test　measurement,　it　was　found　that　the　strong　coupling　of　high-low　pressure　system　caused　single　cylinder　and　multi-cylinder　cycle　injection　quantity　fluctuation　and　abnormal　injection　in　the　system　with　long　injection　pipe.　For　resulting　these　problems,　a　decoupling　method　adopting　damping　delivery　valve　and　optimizing　low　feeding　pressure　was　proposed,　and　delivery　valve　key　parameters　and　the　map　of　low　feeding　pressure　threshold　were　calculated　by　AMESim　modeling.　Validation　experiments　show　that　after　adopting　damping　delivery　valve　optimizing,　the　sensitivity　of　high　pressure　system　to　low　pressure　system　is　largely　reduced　and　in　case　of　long　injection　pipe　there　is　not　cavitation　existence　while　IPW　and　injection　rate　shape　varying.　©,　2015,　Chinese　Society　for　Internal　Combustion　Engines.　All　right　reserved.