The invention discloses a low-quality coal pyrolysis device. The low-quality coal pyrolysis device comprises a closed kiln body with a feed hole and a discharge hole, a high-temperature gas pipeline is arranged in the closed kiln body, a low-quality coal advancing and decomposing channel is formed between the high-temperature gas pipeline and the inner wall of the closed kiln body, and a decomposition gas collecting pipe communicated with the low-quality coal advancing and decomposing channel is arranged on the closed kiln body; the low-quality coal pyrolysis device further comprises a high-temperature gas generating device which is communicated with the high-temperature gas pipeline through a high-temperature gas distributing cover, and the high-temperature gas distributing cover is circumferentially connected with the closed kiln body in a sealing mode. According to the low-quality pyrolysis device, the high-temperature gas generating device is arranged and connected with the high-temperature gas pipeline through the high-temperature gas distributing cover, so that the reliability and stability of the low-quality coal pyrolysis device are improved fundamentally.