The invention discloses an optimized construction method for a double-arc tunnel. The optimized construction method for the double-arc tunnel comprises the following steps that temporary support is carried out after a middle pilot tunnel is mechanically excavated by a benching tunnelling method; a structural steel arc frame is installed on the side, close to a first cave, of the middle pilot tunnel, construction of a hanging net, connecting bars, anchor rods and sprayed concrete is carried out, and a primary support structure is formed by installing the structural steel arc frame, the hangingnet and sprayed concrete construction; plain concrete is backfilled integrally on the side, close to a back cave, of the middle pilot tunnel; the first cave is mechanically excavated by the benching tunnelling method, and a primary support is closed to form a ring; and a back cave is mechanically excavated by the benching tunnelling method, and the primary support is closed to form a ring. The optimized construction method for the double-arc tunnel can reduce construction processes, improve the construction speed and effectively reduce the construction cost.