Abstract: With the development of high-precision space exploration missions such as gravitational wave detection and Earth gravity field detection, the accuracy requirements of propulsion systems are further improved, and it is urgent to develop neutralizers with stable output of small current. In this paper, the working stability and electron extraction of carbon nanotube field emission neutralizer were experimentally studied. The current fluctuation characteristics before and after aging were tested, and spearman rank correlation test was used to analyze the correlation between background electric field and current fluctuation. Besides, three kinds of gate with different aperture were used to test the extraction characteristics of the neutralizer, and the influence mechanism of gate aperture on the performance of the neutralizer was analyzed. The experimental results show that aging treatment is helpful to improve the working stability of the neutralizer, and the background electric field of the emitter has a strong correlation with the instability of the emission current. The gate aperture has influence on both emission and extraction performance, and the 1 mm gate aperture has the best performance under experimental conditions. The results can provide some guidance for neutralizer configuration and structure design in propulsion system.