Provided is a method for preventing the accumulation of cylinder oil at scavenging ports of low-speed marine engines. An oil passage is provided on a cylinder wall inside a cylinder. The oil passage includes multiple oil storage grooves processed in a circumferential direction of the cylinder wall. The oil passage is formed by obliquely extending from the inner side of the cylinder wall to the outside of the cylinder in a radial direction of the cylinder. The scavenging ports are uniformly distributed in a circumferential direction of the cylinder wall, and each of the oil storage grooves is correspondingly processed at an upper portion of the scavenging port upper edge of the scavenging port. Each of the oil storage grooves has a shape matching the curved surface of the scavenging port upper edge.