The invention is intended to disclose a main pipeline hot section integrated extrusion forming device. The main pipeline hot section integrated extrusion forming device comprises a fluctuation pipe connection pipe seat side mould, a connection pipe seat-free side mould and an ADS (Automatic Depressurization System) connection pipe seat side mould; the fluctuation pipe connection pipe seat side mould and the ADS connection pipe seat side mould are provided with cavities correspondingly; the fluctuation pipe connection pipe seat side mould and the connection pipe seat-free side mould are connected with first fixing mandrels correspondingly; and the ADS connection pipe seat side mould and the connection pipe seat-free side mould are connected with second fixing mandrels correspondingly. Compared with the prior art, through integrated extrusion forming, the number of steel ingots can be reduced significantly, the manufacturing cost is lowered, the overall economic index is increased, and the machining quantity of a connection pipe seat is reduced obviously; the connection pipe seat has large deformation, and thus can have good grain fineness; rapid forming can be realized; local heating is adopted, so that the influence on the grain fineness of a non-extrusion part is reduced; and the purposes of the main pipeline hot section integrated extrusion forming device are realized.