As an important observation equipment for high-energy gamma rays, the atmospheric Cherenkov telescope usually uses a large-area reflector system to focus and reflect Cherenkov light onto the camera. Because of its large diameter, a single reflector is assembled by dozens of reflectors to form a complete single focusing reflector. The development of its reflector is still based on the traditional grinding technology in China. Although the optical performance of the processed reflector can meet the requirements of use, the reflector is heavy, the risk of filming is high, and the cost of bulk purchase is extremely high, so it is difficult to mass produce. This paper provides a new processing method of spherical reflector: the glass substrate, aluminum honeycomb sandwich and aluminum back plate are bonded and cured by structural adhesive under the force of vacuum negative pressure to form a regular hexagonal composite reflector blank. Preform the glass substrate before bonding, which can basically adapt to the spherical surface and reduce the subsequent grinding workload of the reflector blank. After bonding, the reflector blank is ground, measured and coated to form the composite spherical reflector. The method improves the production efficiency and reduces the production cost. The composite spherical reflecting reflector with this processing method has the advantages of light weight and large specific stiffness, which is beneficial to subsequent installation and splicing, and reduces the processing difficulty and cost of the mounting bracket.