The invention provides a forming device and method of low-expansion high-thermal-conductivity SiCp/Al composite. The device comprises a base. The base is connected with a beam through vertical pillars. A pressurization device is arranged in the middle of the base and connected with a heating furnace through a position adjusting cushion block. An upper pressing block is arranged on the heating furnace, the two ends of the heating furnace are connected with the vertical pillars through sliding holes correspondingly, and the upper end of the heating furnace is connected with balance weights in the base in a pulley guiding mode through suspension wires. An upper limiting stopper and a lower limiting stopper are arranged on each vertical pillar, and the sliding holes of the heating furnace are located between the upper limiting stoppers and the lower limiting stoppers. The low-expansion high-thermal-conductivity SiCp/Al composite is prepared and formed through links including powder mixing, cold pressing forming, atmosphere hot pressing sintering and the like, all the links are conducted under the atmosphere condition, and a vacuum link is not needed. By using the technology, the technique is simple, the process is short, efficiency is high, cost is low, and the forming device and method of the low-expansion high-thermal-conductivity SiCp/Al composite are very suitable for industrialized mass production.