In　this　paper,　the　effects　of　direct　water　injection　(WI)　on　characteristics　of　combustion　and　emission　for　a　hydrogen　(H-2)-fueled　spark　ignition　(SI)　engine　were　experimentally　investigated.　The　experiments　conducted　under　different　amounts　of　water　injection　(AWI)　and　varied　water　injection　timing　(WIT).　The　experimental　results　showed　that　in-cylinder　pressure　decreased,　indicated　thermal　efficiency　(ITE)　increased,　and　the　flame　development　(CA0-10)　and　propagation　(CA10-90)　periods　prolonged　when　AWI　raised.　When　AIW　grew　to　4.5　mg/cycle,　Nitrogen　oxides　(NOx)　expelled　from　the　original　engine　decreased　by　53.7%　when　excess　air　ratio　(lambda)　was　1.15.　Early　WIT　had　positive　effects　on　the　reduction　of　NOx　emissions.　When　WIT　retarded,　in-cylinder　pressure　increased,　ITE　decreased　and　CAO-10　and　CA10-90　shortened,　NOx　emissions　rapidly　increased.　(C)　2020　Hydrogen　Energy　Publications　LLC.　Published　by　Elsevier　Ltd.　All　rights　reserved.