The invention relates to a combustion synergist for natural gas and liquefied petroleum gas used for cutting and welding of metals. The combustion synergist comprises a solvent, a solubilizing agent, a combustion catalyst, a combustion improver and a dispersant. The combustion synergist provided in the invention can substantially improve combustion temperature, heat and speed of industrial fuel gas, enables a high flame temperature, a short preheating time, a fast cutting speed, a smooth cutting surface of metals and no adherent dross to be obtained during cutting of metals, can be fully mixed with industrial fuel gas, promotes complete combustion of industrial fuel gas, does not produce black smoke, residues or pollutants and has the advantages of safety, convenience, environmental friendliness, convenient popularization and application, etc. The combustion synergist can be widely used for a variety of industrial fuel gas and is especially applicable to natural gas and liquefied petroleum gas.