The invention relates to an interdigitated rotor engine. The complete machine comprises four shell components which are arranged side by side and fixed through bolts; in the three cavities of the inside of the rotor engine, the upper and lower cavities are used to hold a rotor assembly, and the middle cavity is used to hold a transmission system composed of an output shaft, an inner sleeve, an outer sleeve and a multiplex gear. By using the interdigitated rotor engine, power transmission can be realized and the alternate transposition and rotation of rotors can be realized so that the volumes of a plurality of cylinders composed of two interdigitated double-vane or four-vane rotors and the shell can change periodically. A gas port on one side of the rotor cavity is used for air admission and air exhaust, a spark plug on the other side is used for ignition, and the engine capable of performing continuous operation can be realized through four strokes.