Marine parts adopt the internal structure design of double row angular contact ball bearings and thickened outer rings, so that the rollers have higher bearing capacity. The roller is made of high-quality bearing steel, which is processed by heat treatment and precision grinding, and filled with high-quality multi-purpose grease with long service life. Metal dust cover or rubber sealing ring shall be used for roller dust prevention. Roller with concentric sleeve and eccentric sleeve can also be provided, and roller made of corrosion-resistant stainless steel can also be provided. The main roller is the main bearing body in the composite roller bearing, which mainly accepts the load in the vertical direction. It is required to have strong wear resistance, corrosion resistance and impact resistance. At the same time, the main roller can also be used as a single direction bearing to reduce the bearing volume and simplify the device structure, because it is a roller bearing with a full roller structure. The assembly method of the composite roller bearing: the side roller is installed inside the shaft head through the mandrel, the main roller is sleeved outside the shaft head, the cover plate is fixed by nuts at the tail of the shaft head, and finally several parts are fixed together.