The invention discloses a pressure reudcing system for fuel gas, comprising fuel gas pipelines which consist of a high pressure pipeline, a medium pressure pipeline and a low pressure pipeline, which are successively connected in the flow direction of fuel gas, wherein, the tail end of the low pressure pipeline is used for connecting with an external combustion apparatus; a relief valve, an air valve, a heat exchanger and a primary pressure reducing valve are connected in series on the high pressure pipeline; the heat exchanger is provided with a hot fluid inlet and a hot fluid outlet, wherein, the hot fluid inlet is used for connecting with an external hot water apparatus, and the hot fluid outlet is used for connecting with an external water storage apparatus; the medium pressure pipeline is equipped with a relief valve and a secondary pressure reducing valve; the low pressure pipeline is equipped with a relief valve and a third pressure reducing valve. Because of the adoption of three-level pressure reduction, the invention can guarantee output of natural gas with pressure values meeting combustion requirements. The invention also discloses a natural gas dewaxing vehicle employing the fuel gas pressure reducing system for fuel gas, making it possible to use natural gas without enlarging the volume of a vehicle; besides, the cost is low, therefore, the natural gas dewaxing vehicle is applicable to the transformation of the existing vehicles.