Material goes through the feeding device into the lining of the rotary drum, in order to realize the downstream drying, material inner constantly grabbed, scattered under the copy board of a spiral rolling to realize heat exchange, the material move to the other side of the lining and into the middle side, at this time going counterflow drying, material in the middle are constantly repeated by copy board, it is marching into two steps forward and one back, material in the middle is fully absorb heat coming from the inner cylinder, and absorb the middle roller heat and prolong the drying time again at the same time, at the moment dry material is at the best condition. The material go to the other side of the middle section and into the outer section, material within the outer cylinder in rectangular loop travel , in order to achieve the material moving fast to discharge roller under the effect of drying in hot air . Because of the weight other wet material can't advance rapidly drying, the material returns to this rectangular copy board with fully drying action, in this way it can achieve purpose of drying.