Abstract: In order to increase the growth rate of diamond film deposition by hot filament CVD, the filament, the substrate and the gas were limited in a narrow space with a self-made semi-enclosed space restraint device. Acetone and hydrogen were used as the reaction gas source. The deposited diamond films under different gas flow rates were characterized by SEM and Raman spectroscopy. Results showed that the deposition rate could be significantly improved by restraint device. In this experiment, the maximum deposition rate of 6.31 μm/h was obtained at a gas flow rate of 230 sccm, which was nearly two times that of the unconstrained method. As gas flow rate increased, the deposition rate increased first and then decreased. The grain size was micron level at gas flow 86 to 115 sccm, while it changed to nano size at gas flow 115 to 575 sccm. The Raman spectroscopy showed that the quality of the constrained deposited film was generally better, and gradually decreased with the increase of gas flow rate.