The invention provides a coking-prevention light oil yield increasing agent for a delayed coker of an oil refinery. The coking-prevention light oil yield increasing agent comprises the following raw materials in percentage by mass: 35-37% of high-temperature-resistance antioxygen, 13-15% of high-temperature-resistance clearing agent, 10% of high-temperature-resistance dispersing agent, 5% of high-temperature-resistance metal deactivator, 5% of surfactant and 30% of solvent naphtha, wherein the high-temperature-resistance antioxygen is at least one of 2,6-di-tert-butyl catechol, 2,6-di-tert-butyl-p-cresol and 2.6-di-tert-butyl-ethylphenol, the high-temperature-resistance clearing agent is high-base-number linear alkyl benzene sulfonic acid calcium, the high-temperature-resistance dispersing agent is polyisobutylene bissuccinimide, the surfactant is fatty amine polyoxyethylene ether, the high-temperature-resistance metal deactivator comprises at least one of the following inorganic antimony compounds: antimony pentoxide, colloidal solution of antimony pentoxide, antimony pentasulfide, antimony sulfate, or the high-temperature-resistance metal deactivator comprises at least one of the following organic antimony compounds: stibium mercaptide, tricarboxylic antimony, triphenyl antimony, antimony diisopropyl dithiophosphate. The coking-prevention light oil yield increasing agent can be applied to the delayed coker of the oil refinery, the coking resistance rate is higher than 85%, and the yield of light oil is improved by over 1.5%.