The　control　of　the　rail　pressure　is　quite　important　for　a　common　rail　(CR)　fuel　system　since　the　precise　rail　pressure　control　is　the　basis　of　optimization　for　many　controlling　parameters　for　CR　fuel　system,　and　has　a　great　impact　on　engine　power　and　emissions.　This　paper　presents　the　experimental　investigation　of　rail　pressure　characteristics　of　a　CR　fuel　system.　The　rail　pressure　was　tested　in　varied　operation　conditions　with　different　boundaries　and　control　parameters.　The　transient　rail　pressure　characteristics　were　acquired.　Furthermore,　the　pressure　fluctuation　was　analyzed　by　means　of　frequency-domain　method.　This　research　shows　that　the　pressure　fluctuation　in　the　fuel　rail　is　induced　by　fuel　pump　and　injectors　but　not　the　flow　measurement　unit.　©　(2012)　Trans　Tech　Publications,　Switzerland.