In a Bi2O3-B2O3-ZnO glass system, glass structure change, sintering behavior and resultant physical characteristics of the glass were examined when various amounts of Bi2O3 and ZnO mixture were added. When the total amount of Bi2O3 and ZnO was below 30 mol%, a phase separation occurred and homogeneous glass was not obtained. The fraction of four-coordinated borons (BO4) was highest when the total amount of Bi2O3 and ZnO was 50mol%. Further addition over 50 mol% induced a borate anomaly phenomenon in the glass, which resulted in the decrease in BO4 fraction. The sintering temperature and glass transition temperature decreased as the amount of Bi2O3 and ZnO increased. The thermal expansion coefficient and dielectric constant of the specimens were also examined.