By coating the surface of honeycomb ceramic substrates with a catalyst, more than 90% of methane (CH₄) in the exhaust gas of natural gas engines can be efficiently oxidized. Meanwhile, carbon monoxide (CO) and hydrocarbons (HC) are converted into carbon dioxide (CO₂) and water (H₂O). When combined with selective catalytic reduction (SCR) technology, nitrogen oxides (NOₓ) can also be reduced to nitrogen (N₂), realizing the synergistic purification of "methane + NOₓ + CO + HC" and meeting the strict requirements for methane emissions from natural gas vehicles specified in emission regulations.