The connecting rod body is composed of three parts, and the part connected with the piston pin is called the small end of the connecting rod; The part connecting the crankshaft is called the big end of the connecting rod, and the part connecting the small end and the big end is called the connecting rod body.

The small end of connecting rod is mostly of thin-walled ring structure. In order to reduce the wear between connecting rod and piston pin, thin-walled bronze bushing is pressed into the small end hole. Drill holes or mill grooves on the small head and bushing to make the splashed oil foam enter the mating surface of the lubricating bushing and piston pin.

The connecting rod body is a long rod, which is also subject to large force in work. In order to prevent its bending deformation, the rod body must have sufficient stiffness. For this reason, the connecting rod body of vehicle engines mostly adopts I-shaped section, which can minimize the mass when the rigidity and strength are sufficient. H-shaped section is used for highly strengthened engines. Some engines use the small end of the connecting rod to spray oil to cool the piston, and a longitudinal through hole must be drilled in the rod body. In order to avoid stress concentration, the connecting part between the connecting rod body and the small end and the big end shall adopt large arc smooth transition.

In order to reduce the vibration of the engine, the mass difference of the connecting rods of each cylinder must be limited to the minimum range. When the engine is assembled in the factory, it is generally grouped according to the mass of the large and small ends of the connecting rods in grams. The same group of connecting rods is selected for the same engine.

On a V-type engine, the corresponding cylinders in the left and right rows share a crank pin. The connecting rods are of three types: parallel connecting rods, fork connecting rods, and main and auxiliary connecting rods.