Abstract: Residual thermal stress of functionally graded polycrystalline diamond compact in manufacturing process is calculated with the finite element method.The influence on the maximum stress of the volume distribution exponent (n) and the coatings are analyzed.It is showed that the best volume distribution exponent (n) is 1.2,and the number of the coatings is 6.The axial tensile stress in functionally graded polycrystalline diamond compact is reduced from 986 MPa to 323 MPa compared with two layer polycrystalline diamond compact,and the shear stress is reduced from 722 MPa to 454 MPa.In addition,the stress distribution is improved in the interface of functionally graded PDC,and bond strength is greatly increased.