Abstract.The cobalt(II) diethylenetriamine ([Co(dien)2]2+) complex is a newly developed metal thiochelate for the removal of NO from flue gas. The performance characteristics of NO absorption into [Co(dien)2]2+ solution were studied in a stirred reactor. The experimental results showed that this absorption could be regarded as fast pseudo-mth-order reaction and the reaction rate could be expressed as second-order with respect to NO concentration and first-order with respect to [Co(dien)2]2+ concentration. The enhancement factor was 1609.1 at the [Co(dien)2]2+ concentration of 0.01 mol/L. Its optimal absorption conditions were temperature 50 ℃, NO concentration 540 ppm, [Co(dien)2]2+ concentration 0.02 mol/L and O2 concentration 6%, which were determined by orthogonal experiment.