In this paper, we have presented a new type of RF excited diffusively cooled all-metal slab waveguide CO2 laser. In this laser structure, the four side walls of the slab waveguide are all made of aluminum alloy instead of ceramic and metal sandwich waveguide structure in the past technique. In our approach, a low cost of slab waveguide CO2 laser can be achieved. By using the technique in this paper, over 100 watts of laser power has been achieved from a laser head with dimension of 150mm height, 150mm width and 450mm length, which has the slab waveguide gas discharge region of 2mm height, 20mm width and 386mm length. The electro-optic conversion efficiency is over 12%. In our experiment, a gas mixture of CO2: N2: He: Xe =1: 1: 3: 0.26 has been employed, and the gas pressure is in the range from 6.5 Kpa to 13.5 Kpa. The frequency of the RF power is 91.5 MHz, and the RF power is in the range from 500watts to 1000watts.