The amorphous SiO2 filled PTFE composite materials were prepared by using the technology similar to the powder metallurgy.The thermal and dielectric properties of the composites were measured.Also,the microstructure evolution of the composites was characterized by the scanning electron microscopy (SEM).The effects of the different x value (x is the mass ratio,x=0.35,0.40,0.45,0.50,0.55) on the microstructure and dielectric properties of (1-x) PTFE xSiO2 composite dielectric material were investigated.It was found that the density of the composite decreased as the content of SiO2 increased. On the other hand,the water absorption,thermal expansion coefficient,dielectric constant and dielectric loss were increased with the SiO2 content increasing.When the content of SiO2 reached 50%,PTFE could be well coated by the SiO2 layers,and the composites showed suitable thermal expansion coefficient (17 μ℃-1),dielectric constant (2.74) and low dielectric loss (0.002 4).