The film morphology of polycrystalline diamond was observed under a wide variety of conditions by an advanced hot filament chemical vapor deposition (AHF-CVD) method. The main advantage of AHF-CVD is the independent and accurate controllability of CVD parameters, especially of the substrate temperature. Clear faceted planes were obtained under the conditions of higher filament temperature (2000-2100 ℃), pressures of 30-300 Torr, lower methane concentration (≦～1.2%), lower gas flow rate (≦800 sccm), shorter distance between the filament and substrate (≦10mm), and lower substrate temperature (≦910 ℃). At higher pressures of 200-300 Torr, the facets bocame (100)-domiant. The development of (111) and (100) crystal habits was examined with respect to the concentration of the chemical species in the gas phase as estimated by numerical simulation. A key parameter governing the crystal habit was found to be the concentration ratio of H to CH3, or H / CH3 ; the (111) face developed at higher H / CH3 , while the (100) face could dominantly develop at lower H / CH3 . Both the (111)- and (100)-orientation of the films are then discussed in terms of the reconstruction of the growing surface and the contribution of this H ratio.