Piston ring group structure and diesel engine

The utility model discloses a piston ring group structure and a diesel engine, belongs to the technical field of piston equipment, and solves the problems that the resultant force of gas force and elastic force acting on a piston ring in the prior art can cause the phenomenon of radial collapse of the piston ring, and the gas leakage of the piston is easily increased due to long-time radial collapse of the piston ring. The piston ring set structure has the beneficial effects that the collapse duration of piston rings is prolonged, the collapse air leakage is greatly reduced, and meanwhile, the local contact stress of the lower end face of a first piston ring is reduced. A first piston ring groove and a second piston ring groove are sequentially formed in the circumferential side of the piston body in the axial direction of the piston body, the first piston ring groove is a trapezoidal ring groove, the first piston ring is arranged in the first piston ring groove, the second piston ring groove is a rectangular