Polycrystalline diamond bits have the widest application in oil and gas drilling and deep formation drilling. Polycrystalline diamond compact （PDC） consists of a polycrystalline diamond layer and a cemented carbide substrate. Due to the difference in the coefficient of thermal expansion between the polycrystalline diamond layer and the tungsten carbide matrix， there is a huge residual stress inside the PDC after sintering and cooling. To solve the problem of reducing the residual stresses inside the PDC， this paper reports a preparation technology for gradient structure diamond compact. Through the process of fused deposition modelling and sintering （FDMS）， the technical route for the preparation of gradient structure diamond compact was determined； the micro-morphological features of the prepared gradient structure diamond compact and the distribution of the residual stresses were analysed； and the indoor drilling tests were carried out to verify the drilling performance of the gradient structure diamond compact. The results show that the gradient structure diamond compact prepared by the FDMS has a compressive stress of 1.4GPa at the interface between the polycrystalline diamond layer and the gradient layer， which significantly improves the interlayer bonding ability and effectively reduces the internal residual stress， and improves the drilling efficiency by about 36% and the service life is longer compared with that of the conventional compact.