The　performance　of　a　hydrogen-blended　gasoline　direct　injection　engine　under　various　second　gasoline　direct　injection　timings　is　investigated　on　a　modified　commercial　gasoline　direct　injection　engine.　All　tests　are　carried　out　at　a　typically　congested　city-driving　condition　using　lean　burn　and　split　gasoline　direct　injection　modes.　Results　show　that　under　pure　gasoline　fuel　supply　mode,　brake　mean　effective　pressure,　brake　thermal　efficiency,　flame　development　period,　flame　propagation　period,　and　maximum　in-cylinder　pressure　vary　obviously　with　various　second　gasoline　direct　injection　timings　and　the　best　second　gasoline　direct　injection　timing　for　engine　performance　is　130　CAD　before　top　dead　center.　Blending　hydrogen　could　weaken　variations　of　engine　performance　related　parameters　caused　by　changing　second　gasoline　direct　injection　timing　compared　to　that　under　pure　gasoline　mode.　Besides,　blending　hydrogen　could　also　reduce　flame　development　and　propagation　periods,　and　enhance　the　maximum　in-cylinder　pressure　under　the　same　second　gasoline　direct　injection　timing.　With　hydrogen　addition,　the　coefficient　of　variations　in　indicated　mean　effective　pressure　drops　to　less　than　1.1%,　but　second　gasoline　direct　injection　timing　has　no　obvious　effect　on　it　any　more.　Besides,　adding　hydrogen　could　reduce　hydrocarbon　and　carbon　monoxide　emissions　by　33.10%　and　18.28%　in　average,　respectively.　Particulate　number　has　a　reduction　of　order　of　magnitudes　(similar　to　10(8)　to　similar　to　10(6)　n/cm(3)　in　average).　With　hydrogen　addition,　nitrogen　oxides　emissions　increase.