Provided is a self-lubrication system of a power takeoff, comprising a casing (10) and a driving gear (20), a transition gear (30), and an output gear (40). The bottom of an inner cavity of the casing (10) is provided with an oil sump filled with lubricating oil. The lower portion of the driving gear (20) is immersed in the oil sump. An oil nozzle (71) is provided on the casing (10) at a position corresponding to a meshing point between the output gear (40) and the transition gear (30). The output gear (40) rotates in a direction from a lower end point of the output gear (40) to an upper end point of the output gear (40) via the meshing point between the output gear (40) and the transition gear (30). The oil sump is provided at the bottom of the inner cavity of the casing (10) and the oil nozzle (71) is provided on the casing (10) at the position corresponding to the meshing point between the output gear (40) and the transition gear (30), such that a centrifugal force caused by the rotation of the driving gear (20) and the output gear (40) guides the lubricating oil to lubricate the driving gear (20) or the output gear (40) and a corresponding bearing. The system features a simple structure and process, low processing difficulty, and a good lubrication effect.