The invention provides a deep geothermal energy development method. The deep geothermal energy development method comprises the following steps of (1) establishing a vertical shaft wellhole until the vertical shaft wellhole reaches a target stratum, and laying an injection pipeline and a collection pipeline in the vertical shaft wellhole; (2) establishing a horizontal injection tunnel communicating with the injection pipeline and a horizontal collection tunnel communicating with the collection pipeline in the target stratum; (3) establishing a plurality of circulation channels at intervals in the portion, between the horizontal injection tunnel and the horizontal collection tunnel, of the target stratum to enable the inlet end and the outlet end of each circulation channel to communicate with the horizontal injection tunnel and the horizontal collection tunnel correspondingly; and (4) injecting a liquid medium into the injection pipeline to enable the liquid medium to go into the circulation channels through the horizontal injection tunnel to absorb geothermal energy in the target stratum, and then collecting the liquid medium absorbing the geothermal energy from the collection pipeline. By means of the method, the number of bored wells and the occupied area of a ground platform are reduced, the porosity and permeability of hot dry rocks are guaranteed, and the output quantity of geothermal energy is increased.