The development of heavy oil field encounters such problems as steam channeling, water cut rising, and a large number of low production and low efficiency wells. In view of the existing problems, this paper proposed low temperature thermochemistry technique. The chemical system (sulfonate chemical system L⁃B) was developed independently and adapted to the offshore heavy oil field, which was used to synergize the thermal effect of low temperature steam, so as to reduce the cost and increase the efficiency of oil displacement and improve the efficiency of oil displacement. The static oil washing efficiency of the chemical system is 28.7%. The interfacial tension between crude oil and chemical system is 0.086 mN/m at 56 ℃, which is 99.3% lower than that between crude oil and formation water. The displacement efficiency can reach 65.00% at 120 ℃, which is 8.50% higher than that of steam flooding at the same temperature and achieved the steam injection effect at 200 ℃.After the application on an oilfield in Bohai Sea,the maximum daily oil production of a single well can reach 32 m3, increasing 52.4%. Low temperature thermochemical technique has certain guidance and reference significance for enhancing oil recovery of offshore heavy oil field.