The invention discloses a method and a device for forming a special cellular board. The method comprises a step of adopting a fluid to apply pressure to the cellular board paved on a template; and the device comprises a special template, and a sac body for applying pressure to the cellular board paved on the template through the fluid. Because the fluid is adopted to evenly apply pressure to the cellular board paved on the template, the cellular board can be gradually adhered to the template under the even pressure of the fluid until the cellular board has a structure of the template through plastic deformation and the process only needs a side template; and compared with the conventional stamping forming processing with male and female dies, the method and the device reduce the number ofdie bodies in the processing, save the material cost, save the work hours for processing the dies, reduce the processing difficulties caused by adopting the male and female dies, improve the quality of formed products, and improve the efficiency.