The work aims to improve cutting performance and machining efficiency of coated cemented carbide tools in machining titanium alloy. Chemical mechanical polishing (CMP) was applied to polish and pre-treat rake face of cemented carbide YG8 turning insert which has been grinded, and coatings were prepared by adopting CVD and PVD coating processes. Insert durability test of cutting TC4 titanium alloy was performed to polished and coated cemented carbide inserts in single factor test method. Law of influence of tool category and cutting parameters variation on insert durability in the process of titanium alloy machining was analyzed. Wear mechanisms of the inserts were analyzed with scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). After the treatment of chemical mechanical polishing, average roughness of the cemented carbide inserts decreased by 78.2% from 87 nm to 19 nm. Given by same cutting parameters, durability of the polished CVD cemented carbide insert increased by 75% to a maximum extent than that of the grinding CVD cemented carbide insert, and the durability of polished PVD cemented carbide insert increased by 8.3% to a maximum extent than that of the grinding PVD cemented carbide insert. It could be concluded that applying chemical mechanical polishing to cemented carbide insert was an important way of improving surface smoothness and durability of insert. Durability of the polished CVD cemented carbide insert is superior to that of grinding CVD cemented carbide insert, and the durability of polished PVD cemented carbide insert is superior to that of grinding PVD cemented carbide insert.