Rotary　engine　generally　sustains　poor　fuel　economy　and　emissions　performance　at　idle　condition.　Hydrogen　has　excellent　physicochemical　properties　that　can　serve　as　an　enhancer　to　improve　the　performance　of　the　original　engine.　In　this　paper,　a　modified　rotary　engine　equipped　with　dual　fuel　(hydrogen　and　n-butanol)　port　injection　system　and　electronic　ignition　module　was　developed　to　explore　the　influence　of　hydrogen　supplement　on　enhancing　the　idle　performance　of　n-butanol　rotary　engine.　In　this　study,　the　engine　was　run　at　the　idle　and　stoichiometric　with　the　original　spark　timing.　Hydrogen　volume　percentage　in　the　total　intake　was　gradually　increased　from　0%　to　7.9%　by　adjusting　the　fuel　flow　rate　of　n-butanol.　The　experimental　results　indicated　that　the　engine　instability　and　fuel　energy　flow　rate　were　both　reduced　by　enlarging　the　hydrogen　supplying　level.　Combustion　periods　were　shortened　thanks　to　the　enrichment　of　hydrogen.　The　peak　chamber　temperature　was　heightened　as　hydrogen　fraction　increased　due　to　the　improved　combustion.　HC　and　CO　emissions　were　severally　reduced　by　50.4%　and　85.8%　when　the　hydrogen　volume　percentage　was　raised　from　0%　to　7.9%.　However,　NOx　emissions　were　mildly　increased　because　of　the　raised　chamber　temperature　by　increasing　hydrogen　fraction.　(C)　2018　Hydrogen　Energy　Publications　LLC.　Published　by　Elsevier　Ltd.　All　rights　reserved.