A flexible shearing thickening polishing (STP) method can be used to polishthe rake surfaceof the cemented carbide insert with arcchipbreakerto reduce theroughnessofthe rakesurfaceandimprovethe cutting performance of the insert. The method utilizes the shearing thickening effect of non-Newtonian power-law fluid and the micro-cutting effect of abrasive particles to remove the micro-convex peaks on the rough surface of the workpiece. The surface roughness of the chipbreaker of the cemented carbide insert rake surfaceisused as the evaluation index. The Taguchi method is used to design the orthogonal experiment, and the influence of polishing speed, abrasive concentration, abrasive particlesize and inclination angle on the surface roughness of the insertrake surfaceisanalyzed. The analysis of variance (ANOVA) method, which is used to evaluate the effective weight of each factor, shows that the largest affecting factor forthe surfaceroughnessis the polishing speed (74%), followed by the abrasive particle size (11%), the abrasive concentration (11%) and theinclination angle (4%). Under the optimized processparameter combination:polishing speed 85 r/min, abrasive concentration 9wt%, inclination angle 2° and abrasive particlesize #8000, the surface roughness decreases from (120±20) nm to (7.2±0.6) nm, the rough micro-convex peaksbecome smoothand the cutting edge is complete without defects. Compared with traditional brush polishing method,STP method can realize higher efficiency and better quality for polishing the rake surface of the cemented carbide insert. By optimizing the polishing process parameters, the surface quality of the insert can be effectively improved and no defects are caused on the cutting edge. The result shows that the STP is a promising method for the efficient and high-quality polishing of the cemented carbide insert.