The invention discloses a combined pipeline. The combined pipeline comprises an outer layer pipe, an inner layer pipe and circumscribed pipes, wherein the outer layer pipe is connected with the inner layer pipe, and the inner layer pipe is arranged on the inner side of the outer layer pipe; the outer layer pipe is connected with the circumscribed pipes, and the circumscribed pipes are arranged on the surface of the outer layer pipe; shunting openings are formed between the outer layer pipe and the circumscribed pipes; the diameter of one side of the inner layer pipe is greater than that of the other side of the inner layer pipe. According to the invention, the circumscribed pipes of the combined pipeline have a shunting function, a water outlet can be used for draining away water, other shunting openings can be used for discharging slag and the like; the combined pipeline is attractive in appearance and easy to operate.