Experiments　of　a　pure　gasoline-fueled　engine　and　a　hydrogen-enriched　gasoline　engine　with　hydrogen　volume　fractions　in　the　total　intake　of　1%,　3%　and　5%　were　conducted　on　an　engine　test　bench　at　stoichiometric　condition,　respectively.　Simulation　models　for　gasoline　and　gasoline-hydrogen　mixture　fueled　engines　were　built　based　on　AVL　Boost　and　calibrated　with　the　measured　combustion　pressure,　intake　gas　flow　and　brake　mean　effective　pressure　(BMEP)　data　from　the　tests.　The　simulation　study　was　done　at　the　same　intake　manifolds　absolute　pressure　(MAP)　with　different　hydrogen　volume　fractions　in　the　intake　and　various　spark　timings　to　investigate　combustion　characteristics　of　a　hydrogen-enriched　gasoline　engine.　The　simulation　results　showed　that　the　effect　of　hydrogen　addition　on　improving　the　engine　combustion　was　more　pronounced　at　low　load　conditions.　The　flame　development　and　propagation　durations　were　reduced　with　the　increase　of　hydrogen　enrichment　level　when　hydrogen　volume　fraction　in　the　intake　was　below　5%.　The　maximum　BMEP　was　achieved　when　hydrogen　volume　fraction　in　the　intake　was　2%.　For　a　specified　hydrogen　addition　fraction,　cylinder　pressure　first　increased　and　then　decreased　with　the　advance　of　spark　timing,　and　achieved　the　peak　value　when　spark　timing　was　set　to　be　13°CA　BTDC.　The　simulation　results　also　showed　that　the　cylinder　pressure　rise　rate　and　combustion　noise　were　increased,　and　the　relevant　crank　angle　for　peak　cylinder　pressure　was　getting　close　to　the　TDC　with　the　increase　of　hydrogen　addition　level,　so　the　ignition　timing　should　be　delayed.