The invention relates to a method for producing synthesis gas with carbon powder and natural gas/methane as raw materials. The method comprises the steps that carbon powder, natural gas/methane and gasifying agents are subjected to co-gasification reaction at the temperature of 1200-1500 DEG C and the pressure of 1.0-10.0 MPa, the resultant of reaction is subjected to chilling and heat exchange through a cooling system, solid ash is drained to the outside, the synthesis gas product is subjected to ash removal and cooling processing through a Venturi scrubber and a wet ash removal tower, high-concentration synthesis gas is obtained, the volume content of CO+H2 in the synthesis gas is 85.0-95.0%, the content of H2 is 43.0-68.0%, and carbon black water drained from a reaction furnace and the bottom of the wet ash removal tower is drained to a black water treatment workshop section to be treated. The method is wide in range of raw materials, large in production capacity, clean, environmentally friendly, and suitable for multi-line production of industrial large-scale raw material gas preparation.