In　this　paper,　the　effects　of　direct　water　injection　(WI)　on　characteristics　of　combustion　and　emissions　for　a　hydrogen　(H-2)-fueled　spark　ignition　(SI)　engine　were　experimentally　investigated.　The　experiments　were　conducted　under　different　excess　air　ratios　(lambda)　and　ignition　timing　(IT).　In　each　test,　the　water　to　air　ratio　(alpha)　was　varied,　and　the　results　were　compared　with　baseline　data　without　WI.　The　experimental　results　showed　that　incylinder　pressure　decreased,　indicated　thermal　efficiency　increased,　and　the　flame　development　and　propagation　periods　prolonged　when　WI　was　used.　When　alpha　increased　to　1.87%,　NOx　emissions　expelled　from　the　original　engine　separately　decreased　by　36.9%　and　55.4%　when　IT　were　5　degrees　CA　BTDC　and　15　degrees　CA　BTDC　at　lambda　of　1.15.