The invention provides a foam oil displacement system with ultralow interfacial tension and a use method of the foam oil displacement system. The oil displacement system is formed by mixing raw materials in percentage by weight as follows: 0.1%-0.3% of a foaming agent, 0.05%-0.15% of an inorganic reagent, 0.01%-0.10% of a foam stabilizer and the balance of water, wherein the foaming agent is dodecyl dimethyl betaine, dodecyl hydroxysulfobetaine, dodecyl hydroxypropyl sulphobetaine, lauramide propyl hydroxysulfobetaine, lauramide propyl betaine, cocamidopropyl dimethylamine oxide, gemini oxidized tertamine, polyoxyethylene dodecanol ether sulfate or sodium dodecyl sulfate; the inorganic reagent is sodium hydroxide, anhydrous sodium carbonate or sodium metaborate; the foam stabilizer is partially HPAM (hydrolyzed polyacrylamide), acrylamide copolymer, PACHV (high-viscosity polyanionic cellulose) or HPMC (hydroxypropyl methyl cellulose).