Fused silica ceramics were prepared by gel-casting molding process. The crystal structure, micro-morphology and dielectric properties of ceramic samples were analyzed by XRD, SEM and electrical network analyzer, and the influencing factors on dielectric properties of fused silica ceramics were studied to provide basis for screening the optimal preparation technology of fused silica ceramics. The results show that quartz ceramic slabs of different thicknesses are prepared and sintered horizontally with certain material preparation, the density of the same square slab decreases from top to bottom along the vertical direction, and the density has a positive correlation with the dielectric constant, for every 0.01 g/cm3 increase in density, the dielectric constant increases by 0.01~0.02. And the density has little effect on the tangent value of the loss angle. For the same slab of the same thickness, the density of the edge and the middle position barely unchanged. For the same slab and the same thickness direction, the dielectric constant does not change much. The rosin in the quartz ceramic slab makes the sample denser and the dielectric constant increases with the increase of the density, the calculated permittivity has a deviation of about 0.03.