A heavy oil thermal recovery method based on a multi-composition thermal fluid in a supercritical state, comprising: injecting a mixing of steam and vacuum gas oil containing Fe(III) aromatic sulfonate dissolved therein into an subterranean formation to preheat the subterranean formation, and extracting light crude oil from the subterranean formation when a temperature of the subterranean formation reaches a required temperature for combustion of heavy oil; injecting the steam and a combustion-supporting gas into the subterranean formation to enable the heavy oil to be ignited and a temperature of the subterranean formation to be reached 600° C.; and injecting a multi-composition thermal fluid formed by mixing a hydrogen donor with water into the subterranean formation to enable the multi-composition thermal fluid to be heated to the supercritical state under heat provided by the combustion of the heavy oil, and extracting crude oil modified by the heavy oil through the multi-composition thermal fluid.