The invention relates to a lubricating system for a rotor engine and belongs to the field of engines. The lubricating system comprises a crankshaft, a bearing, a rotor, a sealing piece and an electronic control unit component, the crankshaft is processed with an eccentric shaft central oil way and an eccentric shaft radial oil way, and an oil way communicated with the crankshaft is radially processed on the inner side of the rotor; the sealing piece comprises a sealing piece substrate, a slider and oil needle integrated member, a one-way valve, a second sealing elastic device, a second sealing elastic device and an electromagnetic valve; a communicating oil way for supplying lubricating oil is processed from an eccentric shaft to the radial sealing piece, and the electromagnetic valve is controlled by the electronic control unit component to realize reliable supply of the lubricating oil. By the lubricating system, reliable and effective oil supply can be realized when the rotor engine rotates, and lubricating of between the eccentric shaft and a bearing and between the sealing piece and a cylinder can be ensured respectively, so that friction wear is reduced, reliable sealing is guaranteed, service life of each of the eccentric shaft, the bearing, the sealing piece and the cylinder is prolonged, and running performance of the rotor engine is improved.