The invention relates to a three-way catalytic converter cleaning reducing agent, which is composed of the following substances in weight percentage: 3-5% of sec-octyl ketone, 23-25% of ethylene glycol butyl ether, 13-16% of 2-ethyl acetic acid, Isopropanol 29‑32%, 1‑Dodecene 5‑7%, Cyclohexane 2‑4%, water balance. Compared with the existing products, the three-way catalytic converter cleaning reducing agent of the present invention has rapid reaction, can fully dissolve carbon deposits and sulfur and phosphorus compounds, dredge the three-way catalytic converter, realize cleaning and reduction of the three-way catalytic converter, and restore the three-way catalytic converter Active, prolong the service life of the three-way catalytic converter, effectively reduce the emissions of carbon monoxide, hydrocarbons, and nitrogen monoxide, and achieve the purpose of reducing exhaust emissions.