Abstract: With glass powder composed of 15wt%B₂O₃-45wt%MgO-35wt%SiO₂-5wt%ZrO₂ (BMSZ) and AlN powder as raw materials, BMSZ glass-AlN ceramic composites containing different glass content (55wt%-80wt%) were prepared by conventional pressureless sintering. The effects of glass content on the sintering performance, thermal properties, dielectric properties and mechanical properties were discussed. The results show that after adding the glass powder into the AlN powder and then being sintered at 775-875℃, the dense composites were obtained. Increasing the glass content properly improved the sintering densification. When the glass content exceeded 70wt%, the addition of glass weakened its role to promote the sintering densification, and deteriorated the thermal conductivity and bending strength of the composite, but appropriately reduced the dielectric loss of the composite. When the glass content was 70wt%, the composite sintered at 825℃ had a dense structure and obtained the best comprehensive performance, with the bulk density of 2.84 g·cm^-3, the relative thermal conductivity of 9.12 W·m^-1·K^-1, the dielectric constant of 7.65, the dielectric loss angle tangent of 1.24×10^-3, and the bending strength of 174.88 MPa.