A connecting rod of an internal combustion engine, including a small end and a shank. The small end employs a flexible structure made of hard material. The hard material is a steel or alloy material having a tensile strength greater than or equal to 700 megapascal. The small end of the flexible structure includes a circular body, a center hole, and a flexible support. The circular body encircles the center hole, and the center hole is a complete circular hole having a constant diameter. The small end matches with a piston pin. The flexible structure of the small end operates to allow an elastic deformation of the center hole along an axial direction thereof produced by cylinder pressure exerted on the piston pin to adapt to a bending deformation of the piston pin along the axial direction.