In this paper, we have prepared microwave dielectric substrate for the high frequency and high speed circuit by using PTFE resin as matrix and the fused SiO2 as filler, through the mechanical mixing, calendaring and hot press sintering. The effects of different dry processes on the microstructure and microwave dielectric properties of the composites were investigated. It was found that the organic matter could be removed in a relatively short time and the inorganic filler and polymer could be dispersed evenly by the rotary evaporation process. The dielectric constant of the sample was 2.92~2.94 and the dielectric loss was 1.3×10-3 after the hot press sintering.