This　paper　experimentally　investigated　the　effect　of　hydrogen　addition　on　the　cold　start　performance　of　a　methanol　engine.　The　test　was　conducted　on　a　modified　four-cylinder　gasoline　engine.　An　electronically　controlled　hydrogen　injection　system　was　applied　to　realize　the　hydrogen　port　injection.　The　engine　was　started　at　an　ambient　temperature　of　25　degrees　C　with　two　hydrogen　flow　rates　of　0　and　189　dm(3)/s,　respectively.　The　results　demonstrated　that　hydrogen　addition　availed　elevating　the　peak　engine　speed　and　cylinder　pressure　during　the　cold　start.　Both　flame　development　and　propagation　periods　are　shortened　after　the　hydrogen　addition.　When　the　hydrogen　volume　flow　rate　was　raised　from　0　to　189　dm(3)/s,　HC,　CO　and　total　number　of　particulate　emissions　within　19　s　from　the　onset　of　cold　start　were　reduced　by　68.7%,　75.2%　and　72.4%,　respectively.　However,　because　of　the　enhanced　in-cylinder　temperature,　NO　emissions　were　increased　after　the　addition　of　hydrogen.　Copyright　(C)　2014,　Hydrogen　Energy　Publications,　LLC.　Published　by　Elsevier　Ltd.　All　rights　reserved.