The work aims to improve the surface quality of TC4 titanium alloy machined with cemented carbide inserts. Chemical mechanical polishing (CMP) technology was adopted to treat the rake face of cemented carbide insert which has been treated with the grinding process by rough polishing, semi-polishing and fine polishing. Under the condition of dry cutting at room temperature and the cooling air at –50 ℃, the orthogonal experiment for the cutting of TC4 titanium alloy with the grinding cemented carbide inserts (grinding inserts) and chemical mechanical polished cemented carbide inserts (polished inserts) were carried out, respectively. The effect of cutting parameters on the surface roughness Ra of TC4 titanium alloy machined with grinding insert and polished insert under the condition of dry cutting at room temperature and the cooling air at –50 ℃ was studied by ANOVA. The machined surface roughness empirical prediction models for grinding and polished inserts in cutting TC4 titanium alloy was established by the multiple linear regression method. After the rake face of cemented carbide insert was pre-treated with rough polishing, semi-polishing and fine polishing, the surface roughness Ra of the rake face of the cemented carbide insert was 19 nm. Under the same cutting parameters, the surface roughness of TC4 titanium alloy machined with grinding insert under the condition of cooling air at –50 ℃ was 35.9% lower than that machined under the condition of dry cutting at room temperature; and the surface roughness of TC4 titanium alloy machined with polished insert under the condition of cooling air at –50 ℃ was 43.5% lower than that machined under the condition of dry cutting at room temperature. The surface roughness of TC4 titanium alloy machined with polished insert under the condition of dry cutting at room temperature was 19.2% lower than that machined with grinding insert; and the surface roughness of TC4 titanium alloy machined with polished insert under the condition of cooling air at –50 ℃ was 28.7% lower than that machined with grinding insert. The surface roughness of TC4 titanium alloy machined with polished insert under the condition of cooling air at –50 ℃ was 54.4% lower than that machined with grinding insert under the condition of dry cutting at room temperature. It can be concluded that the machined surface roughness of TC4 titanium alloy can be effectively reduced with the combination process of using chemical mechanical polishing technology to treat the surface of cemented carbide insert and taking cooling air at –50 ℃ as a cutting medium.