Abstract: Chemical mechanical polishing (CMP) with colloidal silica which is widely used in ULSI was proved to be sufficient to produce the nanoscale roughness on titanium surface. Experiments were done to optimize the polishing process parameters and examine the effect of some slurry parameters, and an optimum Ti CMP slurry with appropriate material removal rate (MRR) as 156.5 nm/min and low average roughness (Ra) as 0.159 nm by AFM was gotten. The results of electrochemical analysis showed that the synergism of adsorption of SiO2 and lactic acid on Ti surface and destructive effect of ammonia and F- to adsorption film was critical to get optimum polishing results. And XPS results supported the planarization mechanism that loose TiO2 oxide layer was formed during polishing process which could be removed efficiently by mechanical grinding of abrasive particles and polishing pad.