Abstract: A Lab-built glass-integrator was developed to fill into the glass-bubble for atomic clock by accurate condensation of ultrapure rubidium vapor.The condensation of Ru-vapor in the environment of the newly-developed integrator with six glass-bubbles was mathematically modeled,theoretically analyzed in Maxwell speed distribution and Langmuir evaporation/condensation theories,and experimentally evaluated.The influence of the condensation-rate and condensation time on the condensation coefficient and precise Ru-mass was investigated for optimization of the condensation conditions.The condensation coefficient,derived by a combination of theoretical calculation and experimental correction,was estimated to be σ≌0.016~0.019.Test results show that the newly-developed integrator is capable of filling R-vapor into the glass-bubble to a precise mass of 300 μg at an accuracy of ± 50 μg.