The invention relates to a bearing lubricating system of a coal mill. The bearing lubricating system aims to solve the problems that in the prior art, when a bearing lubricating system of a coal mill works, the running time of an oil pump is too long, machine abrasion is serious, the oil quantity is frequently adjusted, much oil or less oil or oil breaking occurs, the phenomena of burning a bearing, damaging equipment and influencing environment and safety production occur, due to the fact that field noise is high, much dust exists and the environment is poor, the mind and body of work staff on the work field all the time are hurt, and work efficiency is low. The lubricating system comprises a sponge body, a high-position oil tank, an oil pump, a limit contact device, a floater, a shaft, a low-position oil tank, a first oil inlet pipe, a second oil inlet pipe, a first oil outlet pipe, a second oil outlet pipe, an oil return pipe, a spiral adjusting rod, a press plate, two bearing seats with bearings, two liquid level meters and two liquid level control boxes. The bearing lubricating system is used for bearing lubricating systems of coal mills.