The invention discloses an oil nozzle cleaning agent and a preparation method thereof. The oil nozzle cleaning agent is prepared from, by mass, 5-15% of an additive, 20-40% of solvent oil, 35-50% of xylene, 5-20% of methyl isobutyl carbinol, 2-15% of petroleum ether and 0-0.01% of color mixing powder. The additive is prepared from, by mass, 20-30% of polyether amine, 15-30% of heavy solvent naphtha, 1-10% of light solvent naphtha, 10-30% of polyether glycol, 1-10% of 2-ethylhexanol, 1-10% of trimethylbenzene, 0.5-5% of naphthalene, 0.5-5% of n-propyl benzene, 0.5-5% of polypropylene glycol, 0.05-3% of cumene and 0.01-5% of triethanolamine. The oil nozzle cleaning agent is capable of clearing carbon deposit in oil nozzles to improve oil atomizing effects, and oil consumption reduction, power recovery and improvement of difficulty in cold starting are realized.