A rotating range modulator was designed and manufactured, which is applied to extend Bragg peak of heavy ion beam. Bragg curves of 75MeV/u ¹⁶O and 75MeV/u ¹²C ion beams through this range modulator were measured respectively and two evident spread-out Bragg peaks corresponding to the modulated beams above are shown. In addition, inactivation effect of the modulated 75MeV/u ¹⁶O ion beam at nine different penetration depths on melanoma cells (B₁₆) was measured. Results indicate that lethal effects at the spread-out Bragg peak region are larger than at the plateau of the particle beam entrance.