Abstract: Bearing is one of the key components in mechanical system. Rolling bearings normally fail in the way of surface pits and spalling due to rolling contact fatigue (RCF). Compared to the conventional fatigue failure, the RCF failure is more complicated, involving wear, mulitiaxial fatigue loading, phase transformation in subsurface material, and many others. This leads to the practical service life of bearings much shorter than the designed life. Therefore, improving the resistance to rolling contact fatigue and wear is a big challenge among industries and academia. Surface technology is one of the effective solutions for improvement of surface quality. Diamond-like carbon (DLC) film is a kind of amorphous carbon film similar to diamond. It has low friction coefficient, high hardness, small thermal expansion coefficient and good wear resistance. Extensive investigations have been conducted on DCL film regarding mechanical and tribological properties, such as elastic modulus improvement, adhesive wear resistance, frictional dependence of grapheme and influential factors. However, there has been a very limited work on RCF. And these reported studies focused on fatigue life and failure on macro scale. The failure mechanism and some typical micro scale failure features of DCL film have not yet been well understood. In this study, the DLC film was successfully prepared on martensitic steel using magnetron sputtering technique. RCF tests were carried out for samples with and without DLC film under lubrication on a two-roller machine. The failure mechanism was investigated based on the detailed analysis of surfaces and sections of failed specimens. The failed surfaces and sections morphologies were inspected by using scanning electron microscope. The Raman spectra of the film was characterized by 2000 micro-Raman system. Energy dispersive spectrometer was used to observe the element distribution between DLC film and substrate. The bonding strength between the film and substrate was measured by a scratch tester. The nano hardness and elastic modulus of the film were measured by nano indentation tester. The experimental results showed that the DLC film on the surface of martensitic steel displayed a high hardness and elastic modulus, and a high interfacial bonding strength between the DLC film and the substrate. The DLC film can significantly improve the RCF life. Furthermore, the samples with the DLC worn out showed even longer residual lives compared to the uncoated samples. On the one hand, it was due to the high hardness of the DLC film itself. On the other hand, a carbon-containing transfer film was formed during the repetitious rolling contact process of the DLC film. The transfer film had graphitization characteristics, which acted as a certain lubrication role. The RCF performance of the DLC film samples was influenced by the surface roughness peak of the substrate, contact pressure, sliding ratio, among which the surface roughness peak showed the biggest influence. The thickness of the DLC film was 3 μm, within the range of 15 μm of the maximum stress distribution. Under cyclic contact stress, the micro cracks initiated preferentially at surface roughness peak and resulted in film spalling. With the increasing number of cycles, the film was worn out and the base material was exposed. A large plastic deformation and micro cracks were generated in the surface and subsurface of base material under RCF, which eventually led to surface pits and material spalling.