A pressure reducing system for fuel gas and a natural gas dewaxing vehicle are provided. The pressure reducing system includes fuel gas pipelines which consist of successively connected a high pressure pipeline, a medium pressure pipeline and a low pressure pipeline in the flow direction of fuel gas. The tail end of the low pressure pipeline connects with a combustion apparatus. A high pressure relief valve, a high pressure air feed valve, a heat exchanger and a primary pressure reducing valve subassembly are connected on the high pressure pipeline. The heat exchanger is provided with a hot fluid inlet and a hot fluid outlet, where the hot fluid inlet connects with a hot water apparatus, and the hot fluid outlet connects with a water storage apparatus. The medium pressure pipeline is equipped with a medium pressure relief valve and a secondary pressure reducing valve.