As one of the key technologies in the exploration and development of geothermal resources, the efficiency and effect of DTH hammer drilling largely depend on the performance of the drill bit, especially the quality and life of PDC spherical cutters. In response to the current issues such as low drilling efficiency and short service life due to the breakage, detachment, and severe wear of cutter in air-assisted percussive drill bits. This paper conducts a macroscopic and microscopic analysis of the PDC spherical cutter, investigates the causes of failure and the failure mechanisms, and proposes targeted measures for improvement. The results show that the main failure modes of PDC spherical cutters are tooth fracture, wear and fall off. The main reason for the failure of the cutter is that the cutter is damaged by tangential impact compression and normal tensile stress at the same time, while the poor performance of the cutter material itself, and the combination strength of the diamond layer and the cemented carbide matrix are also important reasons for the failure. In order to improve the performance and service life of PDC spherical cutters, the stress burden of the cutters can be reduced by optimizing drilling parameters and adjusting external operating conditions. In addition, innovation and improvement of the material formulation, structural design and manufacturing process of PDC spherical cutters is also an effective way to improve its impact resistance and wear resistance. Through these comprehensive performance improvement methods, the reliability of PDC spherical cutters can be effectively improved, thus improving the operational efficiency of downhole drilling and the service life of the bit.