Nicotinic acid (NA) has been widely applied to inhibit corrosion on the Co surface in the Co interconnection chemical mechanical polishing (CMP). The insoluble Co(II)-NA complexes can be observed as organic residues on Co surface after CMP. In this work, the effects of different cleaning solution combination between TMAH and three complexing agents (TETA, EDTA and Gly) on removing NA contamination on the Co surface were researched. Electrochemistry, contact angle, X-ray photoelectron spectroscopy and atomic force microscope were applied to explore the cleaning effect and mechanism. The results showed that the synergetic action of 0.15 wt.% EDTA and 0.15 wt.% TMAH had the optimal removal effect and could significantly remove NA contamination on Co surface. In addition, the molecular activity of NA was calculated based on Density functional theory (DFT) to clarify the mechanism of cleaning process. The results showed that the bond between NA and Co2+ was broken and the Co(II)-NA complex film was decomposed under the action of the cleaning solution.