The invention discloses a method for preparing a diamond film through multiple-doped hot filament chemical vapor deposition and a reaction gas conveying device for the method. The method uses silicon, silicon carbide or silicon nitride ceramics, hard alloy and high-melting-point metal materials (including tungsten, tantalum, molybdenum, titanium and the like) as a substrate and adopts a chemical vapor deposition (CVD) method as the deposition means, an organic compound containing Si, an organic compound containing Si and N, an organic compound containing Si and B or an organic compound containing Si, N and B are simultaneously added into reaction gas hydrogen and acetone (or acetone and carbinol) steam to form a multiple-doped system. a submicron or nanoscale diamond film coating is obtained through the reaction, and the coating thickness can be adjusted in a range of 10-50 mum. The diamond film has the characteristics of abrasion resistance, corrosion resistance, high insulation resistance (in a boron-free occasion), smooth surface, small friction coefficient, easy grinding and polishing and the like, namely has the double advantages of a micro-diamond coating and a nano-diamond coating.