The invention discloses an online automatic end sealing machine. The online automatic end sealing machine comprises a pipe supporting frame, a main end sealing machine, pipe overturning devices and pipe sending devices; multiple pipe supporting grooves which are arranged in the length direction of the pipe supporting frame are formed in the pipe supporting frame; groove openings of the pipe supporting grooves are located in the top surface, the left side surface and the right side surface of the pipe supporting frame; the pipe supporting grooves are also arranged at intervals in the width direction of the pipe supporting frame; the main end sealing machine is located at the left end or the right end of the pipe supporting frame; the pipe sending devices are mounted on the front side and the back side, in the width direction, of the pipe supporting frame separately; the pipe sending device located on the front side of the pipe supporting frame is located inside the first pipe supportinggroove; the pipe sending device located on the back side of the pipe supporting frame is located inside the last pipe supporting groove; one pipe overturning device is correspondingly arranged beloweach of the rest of the pipe supporting grooves except the first pipe supporting groove or the last pipe supporting groove; and the pipe overturning devices are mounted on the pipe supporting frame. By the aid of the online automatic end sealing machine, the purpose of online end sealing of the ends of steel-plastic composite pipes can be achieved.