This　paper　experimentally　investigated　the　combustion　and　emissions　performance　of　a　hydrogen　engine　during　cold　start　at　different　excess　air　ratios(λ).　The　experimental　results　showed　that,　when　λ　declined　from　1.54　to　0.72,　the　peak　engine　speed　was　increased　while　the　successful　starting　duration　for　hydrogen　engine　was　shortened　from　2.4　s　to　1.9　s,　the　successful　starting　duration　was　reduced　by　20.8%.　Both　of　the　flame　development　and　propagation　periods　were　shortened　with　the　decrease　of　λ.　In　addition,　NOx　emissions　increased　slightly　at　first　and　then　decreased　gradually　by　decreasing　λ　within　the　first　6　s.　The　average　NOx　emissions　in　the　first　6　s　reduced　by　84.4%.　it　can　be　found　that　the　highest　peak　NOx　emission　and　the　highest　average　NOx　emission　is　found　at　the　condition　of　λ=1.41.　Moreover,　the　emitted　HC　and　CO　emissions　found　in　the　exhaust　manifold　are　increased　with　the　decrease　of　λ　decreased　due　to　the　evaporated　lubricant　oil.　©　2020,　Science　Press.　All　right　reserved.