The invention discloses a large-diameter steel pipe on-line bulk heat treatment system, comprising a quenching part, a tempering part, a transformer, a power source and a transmission system, wherein the quenching part comprises a quenching induction coil, the tempering part comprises a tempering induction coil, the quenching induction coil and the tempering induction coil are both connected with the power source through the transformer, the processed steel pipe is fixed on the transmission system and the axis of the processed steel pipe is parallel to the transmission direction, the quenching induction coil and the tempering induction coil are arranged in order in the transmission direction of the transmission system and are sleeved on the processed steel pipe. According to the invention, the technological problem of large-diameter steel pipe heat treatment is solved, and the control of heating and quenching temperatures of the large-diameter steel pipes is accurate; and the advantages of simple structure, low energy consumption, low production cost, and few lands are achieved.