This　paper　experimentally　investigates　the　emission　performance　of　a　hydrogen-enriched　gasoline　engine.　The　experiment　is　carried　out　on　a　spark-ignited　gasoline　engine　equipped　with　a　hydrogen　port　injection　system　at　a　constant　engine　speed　of　1400　r/min.　Test　results　show　that　properly　increasing　excess　air　ratio　is　beneficial　for　reducing　the　engine　HC,　CO,　and　NOx　emissions.　CO　emission　increases　with　the　hydrogen　volume　fraction　in　the　intake　at　stoichiometric　conditions.　However,　at　lean　conditions,　the　addition　of　hydrogen　is　effective　in　decreasing　CO　and　HC　emissions.　HC　and　NOx　emissions　are　reduced　with　decreasing　spark　advance.　With　the　increase　of　the　intake　manifolds　absolute　pressure,　HC　and　CO　emissions　are　reduced.