A mechanical coke cleaning device for a carbon conversion reactor comprises following devices in sequential connection: a cutting portion, a supporting portion, a fixing ring, a base portion and a transmission device, wherein the cutting portion connects with the supporting portion which is fixedly connected onto the base portion through the fixing ring, and the base portion connects with the transmission device. The mechanical coke cleaning device is advantageous in that, as shown in figure 1, rapid movement of the working part transmission device 5 drives the cutting portion 1, the supporting portion 2, the fixing ring 3 and the base portion 4 to entirely move up and down, so as to clean the coke on sidewalls of the reactor. In such a structure, no extra air is introduced into the reactor, which may neither influence the content of the gas generated in the reactor nor increase the follow-up gas separation work. The coke cleaning device allows a cracking device continue to operate, thereby prolonging the service lifetime of the reactor, improving work reliability, and optimizing the design, operation control and temperature measurement for the reactor.