Abstract: Aiming at the flatness out-of-tolerance caused by the uneven green density distribution of cemented carbide inserts, the compaction process combining with the numerical simulation and experimental methods was optimized. Based on the two-dimensional axisymmetric model, the synergy of bidirectional synchronous compaction mechanism and 1:1 stroke ratio was the key to obtain the symmetric U-shaped density field and to determine the spatial symmetry of density distribution. Three-dimensional finite element model was established to simulate the practical compaction process of inserts, and the density evolution and deformation behavior during sintering were inversely deduced from the density distribution after compaction. The results demonstrate that the “low-center and high-edge” density distribution induced by this process naturally evolves into a stable concave morphology after sintering. The three-dimensional profilometer measurement on fabricated inserts shows that the flatness fluctuation ranges from −0.008 to 0.007 mm with the expected concave feature, which is in good agreement with the simulation results. The proposed method can replace the traditional trial-and-error method, significantly improve the control accuracy of flatness, and reduce the manufacturing cost, providing a reliable scheme for the industrial production of high-precision cemented carbide cutting tools.