The piston ring–cylinder liner system is the main friction component of internal combustion engines, and its frictional properties affect the service reliability of the entire machine. However, it is impossible to study the evolution of the atomic configurations and the intrinsic causes of the friction process during the friction process using macroscopic methods. The frictional properties between the piston ring with the tetrahedral amorphous carbon (ta-C) coating and the cylinder liner of the internal combustion engines under the α-olefin (PAO) base oil lubrication conditions, at different normal loads, working temperatures, and friction velocities, are studied using molecular dynamics simulation. The numerical analysis results show that the piston ring with the ta-C coating in the friction system exhibits excellent frictional properties under the PAO base oil lubrication conditions. When the normal loads are from 30 to 500 MPa, the top and bottom walls have no shear deformation, the friction force fluctuates around 50 nN, and the frictional properties are optimal at 100 MPa. When the working temperature is from 300 to 700 K, the top and bottom walls have no shear deformation, and the temperature of the friction system increases with the increase of the working temperature. Shear deformation occurs in the top wall at a friction velocity of 0.25 Å/ps and the friction forces increase with the increase of the friction velocity. This study provides theoretical support for the frictional design of the piston ring-cylinder liner system. It is helpful to reduce the design cost and improve the performance of the internal combustion engines.