In order to effectively evaluate the measurement errors of air negative ions, this paper analyzes the measurement errors caused by the ion collector, microcurrent measurement and air flow according to the measurement method of air negative ions. In the case that the ion collector is determined, the microcurrent measurement and air flow are the main factors that cause measurement errors. The centralized comparison of instruments and field inspections show that the measurement results of different types of instruments can basically reflect the change trend of negative ion concentration, but the measured values of negative ion concentration are quite different; some instruments exceed 200%. Laboratory simulation tests show that the influence of air humidity on the instrument measurement is small, and the environmental wind speed has a large impact on the instrument measurement.