The invention provides a method for manufacturing a metal substrate by adopting reflow soldering, comprising the following steps: 1, providing a tin-stibium-tin paste, a metal base plate and a PCB (Printed Circuit Board); 2, designing a steel-mesh window-opening graphic according to the PCB and the metal base plate, and adopting a steel-mesh printing method to print the tin-stibium-tin paste on the metal base plate; 3, adopting a soldering jig to bear the PCB and the metal base plate, and providing the pressure size and uniformity required when the PCB and the metal base plate are soldered; and 4, adopting the reflow soldering method, setting the temperature for reflow soldering according to the melting requirement of the tin-stibium-tin paste and the size of the metal base plate, and leading the tin-stibium-tin paste to be melted to solder and laminate the PCB and the metal base plate into the metal substrate. In the method, the ultra-high-temperature tin-stibium-tin paste with heat conduction and electric conduction is adopted to solder the high-frequency PCB and the metal base plate together, and the radio-frequency performance of the high-frequency PCB and the radiating performance of the metal base plate are effectively guaranteed, so that the reliability of the metal substrate is improved, the processing cost is reduced, then non-layering of the PCB and the metal base plate also can be guaranteed when an electronic device is secondarily attached.