三端空气电容是精密测量微弱电流的重要器件之一。本文对三端空气电容存在的一般性问题作了简单介绍,设计制作了一种同轴三端空气电容作为实验室电容标准,经多年实验观测,长期稳定性好于0.3％。一般电容器随着接线方式不同将有较大的分布电容,且当工作人员接近时,也有附加分布电容,这种电容器的电容值就随外界条件变化而变化。在使用电容器的精密测量中, Three-terminal air-to-air capacitance is one of the most important components for precision measurement of weak currents. In this paper, we briefly introduce the general problems of three-terminal air capacitance, and design and manufacture a coaxial three-terminal air capacitance as the standard of laboratory capacitance. After many years of experiments, the long-term stability is better than 0.3%. General capacitor with different wiring will have a larger distribution capacitance, and when the staff close, there are additional distributed capacitance, the capacitance of this capacitor changes with the external conditions change. In the use of precision capacitor measurement,