Abstract: Using sintered B₄C as target material, ternary BCN thin films were synthesized by means of pulsed laser deposition assisted by nitrogen ion beam. The synthesized films were characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. It is found that the synthesized films contain several bonding structures including B-C,N-C,B-N with B-C-N atomic hybridization rather than a simple mixture. The processes involved in and mechanisms responsible for the film preparation were also discussed. The activated nitrogen in the ion beam can be efficiently combined with boron and carbon created from pulsed laser ablation of the B₄C target, resulting in the deposition of BCN film. The assistance of the ion beam also reduces oxygen from being incorporated into the film as impurities. Elevated substrate temperature is beneficial to the incorporation of nitrogen in the film and influences the chemical structure of the film as well.