A production line of large diameter longitudinal welded pipe comprises a material storage table (1), a charging trolley (2), an uncoiler (3), a leveler (4), a shearing and butt welding machine (5), a movable sleeve (6), an edge milling machine (7), a steel plate flaw detector (8), a lifting table (9), a steel pipe forming machine (10), a welding device (11), a pulling device (12), a heat treatment device (13), a cooling device (14), a rigid rolling machine (15), a cut-to-length cutting machine (16) and a discharging rack (17). The production line in the present invention has the advantages including high production efficiency, stable product quality, low manufacturing cost, as well as reliable and convenient operation.