Abstract： Based on the finite volume method (FVM), the substrate temperature distributions in HFCVD diamond films growth on large quantities of drills with the conventional deposition parameters were investigated. The corresponding temperature measurement tests were also conducted, verifying the rationality and correctness of the simulation method and results. Based on the traditional equidistant filament arrangement, the influences of different deposition parameters on substrate temperature distributions were systematically studied, including the filament separation D, filament length L, filament radius r, filament temperature T and filament height H. Furthermore, a novel nonequidistant filament arrangement was proposed to further improve the uniformity of the substrate temperature distribution, and the optimized deposition parameters were finally determined. The diamond coated drills fabricated with such optimized parameters present satisfying uniformity coating quality, further testifying the reliability of the parameters optimization method based on the simulations.