The piston is an indispensable part of the Volvo diesel generator set. The reciprocating motion in the cylinder transmits the force and completes the working cycle of the diesel engine; the piston, the cylinder head and the cylinder together form the combustion chamber, and the piston group acts as a seal to prevent the gas from penetrating into the crankcase, but also restricts the oil entering the combustion chamber. This paper studies and analyzes the common failures of pistons in diesel engines to make the pistons operate reasonably, efficiently and reliably. 1. Piston skirt wear When the piston is working normally, its skirt and the piston pin seat hole form a vertical working surface. Due to the action of side pressure, it directly rubs with the cylinder wall, and the surface produces regular filamentous wear marks. In general, this wear does not affect the normal fit of the piston to the cylinder wall. When the piston is working, because it is equipped with a piston ring, its