The invention discloses a process method for recovering heat energy of backflow waste heat from aluminum oxide autoclave digestion process.Two-stage heat exchangers are arranged in a hot water station. A first-stage heat exchanger is a water-water heat exchanger. A second-stage heat exchanger is a gas-water heat exchanger. The first-stage heat exchanger, as the water-water heat exchanger, is used for recovering backflow waste heat of the process and heating cold water. The second-stage heat exchanger, as the gas-water heat exchanger, serves as an auxiliary spare heat exchanger. The process method for recovering heat energy of backflow waste heat from aluminum oxide autoclave digestion process has following beneficial effects: (1) a reasonable method is utilized for process backflow temperature of the autoclave digestion process in order to be favorable to cyclic utilization and heat energy of waste heat produced by backflow and temperature reduction is recovered; (2) steam consumption of the hot water station used for heating hot water is reduced and operation cost is saved; (3) a system is easy and is convenient to apply, operate and maintain.