The removal of NOx by cobalt ethylenediamine solution has attracted much attention, but its reaction mechanism is still not clear. In this study, the reaction mechanism was analyzed experimentally and through practical engineering experiments for thirteen consecutive days. The results indicate that the removal of NOx by cobalt ethylenediamine solution can be divided into two steps. For industrial applications, the removal of actual flue gas NO by cobalt ethylenediamine absorbent was investigated by a gas‐liquid countercurrent and concurrent system in a glass fiber factory in Neijiang, Sichuan province in China, indicating that the average removal efficiency of NO and NOx reached 80 % and that of SO2 90 %.