The invention relates to a method for preparing a nanocrystalline diamond film by adopting a helicon wave plasma technology. The method comprises the following steps: (1) introducing Ar gas and H2 gas into a discharge chamber, realizing Ar and H2 mixed gas discharge through radio frequency modulated helicon wave plasma in an axial magnetic field environment, and cleaning a substrate holder and a Si substrate; (2) closing H2 gas, introducing Ar gas and CH4 gas, and forming a nanocrystalline diamond film on the Si substrate through the radio frequency modulated helicon wave plasma in the axial magnetic field environment; and (3) cleaning the CH4 gas adsorbed to the surface of the nanocrystalline diamond film. According to the invention, the nanocrystalline diamond film is successfully prepared by the helicon wave plasma technology, the used equipment is simple, the industrial production is easy to realize, the deposition speed is high, and the problem that the filament performance is degraded is solved; moreover, the process steps are simple, and the process parameters are easy to control.