The invention provides a self-lubricating system of a power takeoff. The self-lubricating system comprises a shell, a driving gear, a transition gear and an output gear, and further comprises a transition axle. The output gear is located above the side of the transition gear. An oil nozzle is arranged at the position, corresponding to the engagement point between the output gear and the transitiongear, of the shell. The transition axle is sleeved with bearings and a bearing end cover. The transition gear is sleeved with the bearings. A groove is formed on the shell, and an oil storage cavityis formed between the groove and the bearing end cover. A lubricating channel communicating with the oil storage cavity is formed on the transition axle. The lubricating channel is arranged on the transition axle, the bearings are lubricated through the pressure difference between the lubricating channel and the oil storage cavity, the supply amount of lubricating oil is effectively ensured, and the lubricating effect is relative good; and compared with the technical scheme of arranging an oil way on a shell in tradition, the structure and the process are simple, the machining difficulty is low, and the lubricating is relatively good.