Abstract:   Hot filament CVD method, which is used to synthesize high efficiency and high quality superhard abrasives, has become a research hotspot. Based on a new multi-piece grid substrate, which can increase the single deposition yield of micro-powder, and FLUENT, the fluid simulation software, the traditional model is optimized with unchanged number of single outlet and stable total intake flow but the single inlet is split into five equally sized inlet. The number and the arrangement of inlets that affect the process uniformity are simulated. The physical field of gas in the HFCVD system is compared and analyzed. Results show that the four optimized models all perform improved uniformity of substrate temperature and flow rate, which is conducive to the uniform growth of diamond single crystal particles, but the effect of diamond deposition rate  is not significant. Further analysis on the temperature field of the optimized model indicates that the temperature difference of the system is the lowest with five inlets located in the middle top and a single outlet in the middle bottom of the reaction chamber, which satisfies the condition of uniform growth of diamond single crystal particles on multi-piece silicon substrate. Finally, CVD single crystal diamond particles are deposited to verify the reliability of the simulation.