A downflow catalytic cracking reactor, comprising the following components: catalyst delivery pipe (1), reactor top cover (2), feed nozzle (3), reactor vessel (6), downflow reaction pipe (9), the upper end of the outer body is close connected to top cover (2) along the direction of circumference; the bottom of the outer wall body is close connected to the outer wall of the downflow reaction pipe; the upper section of the downflow reaction pipe is located inside the reaction vessel, while the lower section extends from the bottom of the outer body; feed nozzle (3) is located on the top cover (2) and/or side wall of the reactor vessel (6) with the outlet of the feed nozzle being above the inlet of the downflow reaction pipe; catalyst delivery pipe (1) is fixedly joined to the reactor vessel and in communication with catalyst lifting zone (7) formed by the reaction vessel and the downflow reaction pipe.