Calcium borosilicate (CaO-B2O3-SiO2, CBS) glass based glass-ceramic composites were prepared by introducing borosilicate glass. The effects of borosilicate glass and firing temperature on the microstructure and properties of the glass-ceramic composites were investigated. The results showed that the composites containing 0~40% (in mass fraction, the same below) borosilicate glass can be sintered at 850°C. The dielectric constant (εr) decreases with the increase of borosilicate glass content and can be adjusted in the range of 5.6~6.6. The coefficient of thermal expansion (CTE) increases with the increase of borosilicate glass content. Increasing sintering temperature favors the precipitations of crystal phases, which have lower εr than CBS glass, resulting in the decrease of εr for the composites.