The invention provides a rotor engine and relates to the technical field of engines. The rotor engine comprises a stator and a rotor which are rotatably connected. Stator seats with changeable track annular guiding grooves are arranged at the two ends of the stator. The side wall, close to the rotor, of the stator is provided with a combustible gas input arc-shaped groove, a combustible gas inlet, an annular groove, a burning explosion cavity, a pressure reducing device and waste gas discharging outlets, and a pressure blocking clamp is arranged in the annular groove. The rotor is provided with combustible gas piston cavities provided with combustible gas pistons, sliding block grooves provided with sliding blocks and gas changing channels, the sliding blocks at the same generatrix on the rotor and the combustible gas pistons are fixedly connected to the same sliding rod located in each sliding rod groove, and the two ends of the sliding rods stretch into the changeable track annular guiding grooves on the stator seats correspondingly. The rotor engine can improve work efficiency.