Glass-ceramics with low dielectric constant and low dielectric loss is an important material for the manufacture of low temperature cofired ceramic substrates. CaO-B2O3-SiO2 (CBS) glass-ceramics was prepared by melt-water quenching method, and the effects of m(CaO)/m(SiO2) mass ratio and B2O3 content on the dielectric properties of CBS glass-ceramics were studied. The results show that the main crystalline phases of CBS glass-ceramics are Ca3Si3O9， Ca2B2O5， CaB2O4， SiO2 and Ca2SiO4. The dielectric constant increases, the dielectric loss decreases first and then increases with the increase of m(CaO)/m(SiO2) mass ratio. The increase of wollastonite phase decreases the dielectric loss from 2.87×10-3 to 1.36×10-3. The dielectric loss increases with the increase of SiO2, Ca2B2O5 and CaB2O4 content. With the increase of B2O3 content, the dielectric constant increases first and then decreases， and the dielectric loss is reversed. When m(CaO)/m(SiO2) mass ratio is 0.89 and B2O3 content is 15%(mass fraction)， the coefficient of thermal expansion is 7.16×10-6℃-1， the dielectric constant is 5.85， and the dielectric loss is 1.37×10-3 (10 GHz) after sintering at 900 ℃ for 3 h.