The self-aligning roller bearing is the bearing that between the inner rings of the two raceways and the outer ring taking the raceway as the spherical surface, the drum-shaped rollers are equipped a spherical outer ring between the two raceways of the inner ring raceway assembly with drum-shaped roller bearings. There are two rollers in the self-aligning roller bearing, mainly bearing the radial load. It is also able to withstand the axial load in either direction. The high radial load capacity of the self-aligning roller bearing makes it especially suitable for the overload or vibration load work, but it can not afford the pure axial load. The outer ring raceway of this kind of bearing is spherical shape, thus the aligning performance is so good to compensate the concentricity error.