Abstract: In the process of preparing diamond coated tools by a hot filament chemical vapor deposition (HFCVD) method, substrate temperature has an important effect on the uniformity of diamond coating distribution. FLUENT module in ANSYS software is used to analyze a three-dimensional batch tool model of HFCVD by GAMBIT software. In simulation, three heat transfer approaches, namely conduction, convection and radiation, are considered. The simulated investigation analyzes and optimizes the effect of the heat dissipation mode at the bottom of tools on the distribution uniformity of substrate temperature. According to the results, compared with the traditional copper or graphite holder, the ceramic holder with a low thermal conductivity have the lowest the average temperature difference between tools and holder, about 37.82 ℃, which is 45 ℃ lower than the temperature difference between tools and Cu holder. The ceramic holder will be more conducive to the preparation of uniform thickness and quality of CVD diamond coated tools.