Diamond-like carbon films were synthesized on stainless steel and silicon substrates by a linear ion beam combined with sputtering deposition system. Effect of substrate negative bias and the buffer layers on the microstructure and properties of DLC films was investigated. The results showed that,with the same buffer layer, the number of sp³ bond in the films decreased when the bias voltage changed from -100 V to -200 V, but the hardness and the adhesion strength were enhanced because of a better compactness of the films; on the other hand, with the increasing thickness and number of deposited layers, the number of sp³ bond in the films reduced when the bias voltage was -200 V, meanwhile the hardness of the multilayered film and the thickness of the buffer layer decreased together; the number of sp³ bond in the film and hardness of the DLC films prepared at the bias voltage of -100 V were little affected by the thickness of the buffer layer and number of deposited layers; among others a DLC film of 4.92 μm thick prepared on a 1.7 μm thick buffer layer of Cr/CrC showed the best comprehensive properties, of which the hardness is 29.4 GPa and friction coefficient is less than 0.1.