The utility model belongs to the field of copper and aluminum melting equipment, and relates to a premixing combustion system for a vertical melting furnace, which comprises a fan air supply system, a fuel supply system, three identical fuel gas premixing systems and three identical combustion control systems. The fuel gas premixing systems are the core of the whole premixing combustion system, each fuel gas premixing system mainly comprises an SR pressure reducing valve, a balance valve, a high-flow regulating valve, a micro-flow regulating valve, a mixer and pipelines, wherein the SR pressure reducing valve, the balance valve, the high-flow regulating valve, the micro-flow regulating valve and the mixer are sequentially connected through the pipelines along the natural gas supply direction. The mixers are connected with a heat exchanger through a pipeline with an electric butterfly valve. Each combustion control system mainly consists of a fuel gas check valve and a high-speed burner, and the fuel gas check valves are connected with metal corrugated expansion joints of the fuel gas premixing systems through pipelines. Presently, the energy consumption of domestic vertical copper melting furnaces is 50-60m3/T copper, using the premixing combustion system can reduce the energy consumption to 45m3/T copper and save energy by more than 10%.