Diesel purification synergist and application thereof

The invention discloses a diesel oil purification synergist which comprises the following components in percentage by mass: 0.05-0.5% of ferrocene and an organic oxygen-containing substance, the organic oxygen-containing substance can be mutually dissolved with the diesel oil; the content of the organic oxygen-containing substance enables the oxygen content in a diesel oil product added with the diesel oil purification synergist to be greater than or equal to 2%; the closed-cup flash point of the organic oxygen-containing substance is greater than 55 DEG C; the organic oxygen-containing substances comprise one or more of alcohols, ethers and esters; the alcohol is multi-carbon alcohol with the carbon atom number of more than 6 or an isomer of the multi-carbon alcohol; the ether is one of diethylene glycol dimethyl ether, dicyclohexyl ether, ethylene glycol butyl ether and diethylene glycol ether; the ester is fatty acid methyl ester. When the diesel purification synergist provided by the invention is used for