Oxygen-doped diamond films are prepared by implanting various dose oxygen ions into the diamond films synthesized by hot filament chemical vapour deposition, and their electrical and structural properties are investigated. Hall effect measurements show that lower dose xygen ion implantation is beneficial to preparing n-type diamonds. The carrier concentration increases with the dose increasing, indicating that oxygen ions supply electrons to the diamonds.The results of AES spectrum indicate that oxygen ions are doped into the diamond films, and the O-implanted depth is around 0.1μm. Raman spectrum measurements indicate that the lower dose oxygen ion implantation at 1014 cm-2or 1015 cm-2 is favourable for producing less damaged O-doped diamond films.