A device for assisting the coating of a radial self-sealing tire of trucks and buses, including: a support frame and a positioning frame. Both ends of a top of a side of the support frame are fixedly provided with a first bearing through a bearing seat, respectively. Two first bearings are arranged coaxially, and the positioning frame is rotatably connected between the two first bearings. Two chutes are arranged inside the support frame and opposite to a fixing frame. The two chutes are slidably connected with a sliding connection seat, respectively. A lifting frame is arranged between two sliding connection seats.