The Hoffmann kiln refers to a continuous kiln with an annular tunnel structure, divided into preheating, bonding, cooling along the length of the tunnel. When firing, the green body is fixed to one portion, sequentially add the fuel to the various locations of the tunnel, so that the flame is continuously moved forward, and the body is sequentially passed through three stages. The thermal efficiency is high, but the operating conditions are poor, used for firing bricks, watts, coarse ceramics and clay refractories.