The invention provides a pyrolysis and catalytic cracking reactor which comprises a feeding port, a pyrolysis chamber, a cracking chamber, a cracking gas outlet and heat accumulating type radiant tubes, and further comprises a heat insulating brick wall, a catalyst adding device, and a communicating component, wherein the heat insulating brick wall is arranged at a part about 2/3 of the transverse width of the reactor, and divides the internal space of the reactor into the pyrolysis chamber and the cracking chamber; the catalyst adding device is connected with the cracking chamber; the communicating component is arranged at the lower part of the heat insulating brick wall. Oil gas generated in the pyrolysis chamber of the reactor can enter the cracking chamber for deep catalytic cracking, macromolecular tar molecules are cracked into micromolecular gaseous hydrocarbons, and the reactor can generate a large amount of cracking gas and generate a large amount of hydrogen gas in a catalytic cracking manner, so as to solve the problem that produced pyrolytic tar contains dust, and really realize clean and efficient utilization of fossil fuel. Moreover, two types of operation can be performed in one furnace body, two become one, the building cost is reduced, and the floor space is saved.