The invention discloses a chemical assistant for thermal recovery of thick oil. The chemical assistant is prepared from the following components in percentage by mass: 0.5-10% of alkaline material, 0.05-5% of surfactant, 0.5-10% of alcohol and 75-98.95% of water through mixing and stirring. When the chemical assistant provided by the invention is added under the condition of steam injection in the thermal recovery of thick oil, the viscosity of the thick oil can be greatly reduced, the viscosity reduction rate reaches up to 98%, the fluidity of the thick oil can be improved effectively, and the yield of the thick oil reservoir is improved, and furthermore, the chemical assistant can be widely used in the field of development of thermal recovery thick oil reservoir.