The invention discloses a pyrolysis reactor. The pyrolysis reactor comprises a material inlet, an oil gas outlet, a semicoke outlet, heat accumulating type radiant tubes, a stirring assembly and an exhaust umbrella, wherein the semicoke outlet is formed in the bottom of the pyrolysis reactor, the heat accumulating type radiant tubes are arranged on multiple layers in the height direction of the pyrolysis reactor inside the pyrolysis reactor, a plurality of parallel heat accumulating type radiant tubes are arranged on each layer in the horizontal direction, the stirring assembly comprises a rotatable stirring shaft and a plurality of stirring rods, the stirring shaft stretches into the pyrolysis reactor from the semicoke outlet, the stirring rods are connected to the stirring shaft along the length of the stirring shaft, the stirring rods are located between the layers of the heat accumulating type radiant tubes, the exhaust umbrella is arranged inside the pyrolysis reactor, located above the top layer of the heat accumulating type radiant tubes and communicated with the oil gas outlet in the side wall of the pyrolysis reactor. According to the pyrolysis reactor, materials are uniformly distributed inside the reactor, the pyrolysis effect is good, and the shale oil yield is high.