The invention provides a slag removal device for a gas pipeline. The device comprises a three-way pipe, wherein a gas inlet pipe and a gas outlet pipe of the three-way pipe are connected in series with a gas exhaust pipeline respectively; a lower orifice of the three-way pipe is connected with a box body through a gas guide pipe; a slag removal port with a cover is formed in the bottom of the box body; a valve is arranged in the middle of the gas guide pipe. The slag removal effect is obvious, and certain light rock powder and slag dust are cleared out of the gas pipeline; moreover, smooth and unblocked gas exhaust pipeline is guaranteed, and the gas exhaust efficiency is improved, so that safety guarantee is provided for coal mining.