Selective　catalytic　reduction　with　coal　gas　can　be　a　solution　for　NOx　emission　control　in　the　iron　and　steel　industry;　nevertheless　coal-gas-SCR　is　not　clearly　understood　and　hard　to　study　due　to　the　multiple　reductants　in　coal　gas　(H-2,　CO,　and　CH4).　In　this　work,　Cu-ZSM-5　was　selected　as　a　candidate　catalyst　after　being　compared　with　other　Cu-zeolite　catalysts.　The　activity　evaluations　of　various　SCR　reaction　with　different　reductant　combinations　revealed　that　there　are　interactions　and　synergistic　effects　between　components　of　coal　gas.　Subsequently,　with　the　help　of　TPD,　TPSR,　and　transient　reaction　studies,　the　interactions　between　these　reductants　over　Cu-ZSM-5　were　clarified　and　the　reaction　mechanism　network　of　coal-gas-SCR　was　also　well　established.　We　found　that　H-2　can　enhance　the　CO-SCR　performance　by　promoting　the　NCO　route.　However,　CO　would　restrain　H-2-SCR　through　covering　the　active　sites　by　bicarbonate　species.　Moreover,　NCO　and　efficiently　activate　CH4,　consequently　improving　the　CH4-SCR　performance　following　the　CH3NO　route　at　low　temperature.