Based on the silicon micromachined technology, a W-band 4-way silicon waveguide power splitter/combiner was designed and fabricated in this paper. The silicon waveguide has been realized by dry etching and wafer level bonding on an 8 inch silicon wafer. According to the characteristics of silicon micromachining, a waveguide power splitter/ combiner based on H-plane T-junction and 3dB coupler was designed. This silicon splitter/combiner exhibits extremely low loss. A silicon power combined PA module was developed by using this silicon power splitter/combiner together with four 2W GaN MMICs. The output power is between 7.03W and 8.05W across the frequency range of 92 to 96GHz with an input power of 30dBm, and the typical PAE is 15%. The average combining efficiency is 88%.