Diamond-like carbon films were synthesized on P type Si (100) substrates by an advanced linear ion beam system using the precursor gas of acetylene.Effect of substrate negative bias on the microstructure and properties of DLC films were investigated by Raman spectroscopy,stress tester and nano-indenter respectively.The tribological behavior of films as a function of the bias was also studied by a homemade ball-on-disk tribometer.With increasing the bias from 0 to-200V,it was found that the G-peak position of the raman spectra had a lowest value at the bias voltage of-100V,which represented the highest sp3 fiaction in the DLC films.Correspondingly,the highest residual stress,hardness and Youngs modulus of were also observed when the negative bias voltage was-100 V,respectively.The minimum friction coefficient of 0.05 and the wear depth of film were also indicated at the bias of-100V,which was both correlated with the film microstructure and the formed graphitic transfer layer during the tribelogical test.