The　performance　of　a　hydrogen-blended　gasoline　engine　at　lean　and　the　wide　open　throttle　conditions　was　investigated.　A　hydrogen　port-injection　system　was　adopted　to　introduce　the　hydrogen　into　each　cylinder.　The　engine　was　operated　at　1400　rpm　and　two　hydrogen　blending　levels　of　0%　and　3%.　The　excess　air　ratio　was　raised　from　1.00　to　about　1.45　for　a　given　hydrogen　addition　fraction.　The　test　results　demonstrated　that　the　hydrogen　blending　contributed　to　the　raised　thermal　efficiency　and　shortened　flame　development　and　propagation　durations.　An　increased　brake　mean　effective　pressure　was　found　after　the　hydrogen　addition　only　at　lean　conditions.　For　both　stoichiometric　and　lean　conditions,　the　hydrogen　blending　was　beneficial　for　reducing　the　engine　cyclic　variation.　This　provides　a　possibility　to　run　a　hydrogen-blended　gasoline　engine　with　the　fully　opened　throttle　position　and　control　the　engine　torque　only　by　adjusting　the　excess　air　ratio.　Toxic　emissions　including　HC,　CO　and　particulate　were　reduced　after　the　hydrogen　blending.　(C)　2014　Elsevier　Ltd.　All　rights　reserved.