An etching process of hydrogen ions was performed during the initial growth stage of diamond films, by applying a negative substrate bias. The contribution of H+ etching under different substrate bias voltages and for different etching times to the orientation grade of diamond films was investigated by scanning electron microscopy and atomic force microscopy. It was found that an H+ etching process with only hydrogen as a reactant gas had influence on the orientation grade of deposited [001]-oriented diamond films. The ion etching induced improvement of the film orientation was proved to be dependent on the bias voltage and etching duration. An improvement of film orientation can be achieved by adjusting the bias voltage and the etching time with respect to the growth situation of diamond films.