The work aims to explore the effect of modified film components on performance and provide an effective method of film composition design according to the surface modification requirements for the stainless steel bipolar plate of the proton exchange membrane fuel cell (PEFMC). Firstly, based on the cluster-plus-glue-atom model and the electron orbital saturation principle, the optimal cluster type and the optimal composition of Cr-C binary material system were designed theoretically. A series of CrxC1-x films with different compositions were prepared on the 316L stainless steel bipolar plate by arc ion plating technology. The composition, structure and performance of the film were characterized and analyzed. The optimal cluster formula of the obtained Cr-C material system was [Cr-C4]CrC3, and the corresponding optimal atomic ratio composition formula was Cr0.22C0.78. The composition coefficient x of the prepared CrxC1-x film was between 0.05 and 0.23. The electrical conductivity and corrosion resistance of the film increased significantly with the increase of the component x. Among these films, Cr0.23C0.77 film had the best comprehensive performance: the interface contact resistance was 2.8 mΩ?cm2 under the compaction force of 1.2 MPa and the corrosion current density was only 9.1×10-2 μA/cm2 in the simulated corrosion environment. The performance was better than that required by technical standards of DOE. The composition of Cr-C modified film has an important influence on the conductivity and corrosion resistance. Since the Cr0.23C0.77 thin film with the best performance has basically the same composition as the ideal optimal composition formula [Cr-C4]CrC3 (Cr0.22C0.78) obtained based on the cluster-plus-glue-atom model, it is confirmed that the composition design of the modified film of the bipolar plate based on this model is effective.