The invention relates to a heavy oil viscosity breaking method based on super-critical benzene. The heavy oil viscosity breaking method comprises the following steps: putting heavy oil into a super-critical benzene environment with a specific thermodynamic state (including the temperature of 360 to 400 DEG C and the density of 0.25 to 0.35g/cm<3>) and transferring viscosity breaking of the heavy oil from a high-viscosity oil phase to a super-critical benzene phase; improving and accelerating arene dealkylation, which influences heavy oil viscosity breaking efficiency, through diffusing; according to series macroscopic topological structure characteristics of the arene dealkylation and arene condensation in a heavy oil viscosity breaking process, synchronously preventing secondary arene condensation in a viscosity breaking process through acceleration on the arene dealkylation under a series reaction framework and inhibition of a super-critical benzene medium on arene supramolecular coke aggregation. By adopting the heavy oil viscosity breaking method based on the super-critical benzene, provided by the invention, the viscosity breaking of the heavy oil can be finished at relativelylow reaction temperature and within relatively short staying time; efficient viscosity breaking is realized in the process under the condition that raw material group composition basically keeps unchanged and coking is not caused.