The invention discloses a differential type energy recovery device for a seawater desalination system. The differential type energy recovery device structurally comprises a conversion machine body, asecondary utilization converter, an energy recovery controller, a desalination treating tank body, a water discharging groove, a water feeding pipe and a joining shaft body, wherein the secondary utilization converter is arranged at the right-upper part of the conversion machine body and is connected with the conversion machine body in a locking manner; the right side of the conversion machine body is connected with the joining shaft body in a penetrating manner; the joining shaft body is arranged at the left side of the desalination treating tank body and is welded with the desalination treating tank body; the energy recovery controller is arranged above the desalination treating tank body and is connected with the desalination treating tank body in a fastening manner; the water feeding pipe is arranged at the front side of the desalination treating tank body and is connected with the desalination treating tank body in a locking manner; the water discharging groove is arranged at theright side of the desalination treating tank body and is connected with the desalination treating tank body by screws. The differential type energy recovery device disclosed by the invention has the beneficial effects that when the equipment is used, due to the conversion mechanism arranged on the equipment, the problem that the hydraulic overturning machine in the seawater desalination system cannot be secondarily recycled in the prior art can be avoided and the equipment use is more energy-saving and emission-reducing.