Because　of　the　limit　of　properties　of　gasoline　and　irregular　design　of　chamber,　the　pure　gasoline　rotary　engine　generally　encounters　partial　burning,　increased　noxious　emissions　or　even　misfire　at　lean　conditions.　This　situation　could　be　deteriorated　at　idle　because　of　the　high　variation　in　the　intake　charge　and　low　combustion　temperature.　Hydrogen　addition　is　proved　to　remit　the　deterioration　of　performance　of　sparked-ignited　(SI)　engines　at　idle　and　lean　conditions.　This　paper　conducted　an　experiment　on　a　modified　rotary　engine　equipped　with　gasoline　and　hydrogen　port-injection　systems　to　explore　the　performance　of　a　hydrogen　gasoline　rotary　engine　(HGRE)　at　idle　and　lean　conditions.　An　electronic　management　unit　(EMU)　was　invented　to　manage　spark　and　fuel　injection.　Excess　air　ratio　(A)　and　hydrogen　volumetric　fraction　in　the　total　intake　(alpha　H-2)　were　also　governed　through　the　EMU.　For　this　study,　the　HGRE　was　operating　at　idle　and　alpha　H-2　was　kept　at　0%　and　3%,　respectively.　For　a　specific　alpha　H-2,　gasoline　flow　rate　was　reduced　to　make　the　HGRE　run　at　desired　A.　Results　indicated　that　engine　fluctuation　and　fuel　energy　flow　rate　were　both　decreased　after　hydrogen　addition.　Combustion　duration　was　cut　down　and　central　heat　release　point　was　advanced　after　hydrogen　addition.　Peak　chamber　temperature　(T-max),　pressure　and　heat　release　were　enhanced　after　hydrogen　blending.　HC,　CO　and　CO2　emissions　were　simultaneously　reduced　because　of　hydrogen　enrichment.　Specifically,　at　lambda　=　1.00,　HC,　CO　and　CO2　emissions　were　respectively　reduced　from　42,411　to　26,316　ppm,　1.86　to　0.78%　and　9.96　to　8.58%　when　3%　hydrogen　was　added.　(C)　2017　Hydrogen　Energy　Publications　LLC.　Published　by　Elsevier　Ltd.　All　rights　reserved.