Improved ventilation device

The utility model discloses an improved ventilation device. The fermentation tank comprises a fermentation tank body, a small ventilation groove is formed in the bottom surface of the interior of thefermentation tank body; a supporting table is fixed in the small ventilation groove; a ventilating branch pipe is placed on the supporting table; ventilation holes are formed in the surfaces of the ventilation branch pipes; the end parts of the ventilation branch pipes penetrate through the fermentation tank body and are communicated with a ventilation main pipe; the ventilation main pipe is fixedly connected with an outlet of a fan, a net plate is arranged above the ventilation branch pipe, a dry material cushion layer is arranged above the net plate, the two ends of the net plate are supported through supporting blocks, and the supporting blocks are fixed to the inner wall of the fermentation tank body through bolts. By arranging the dry material cushion layer, the small ventilation grooves, the ventilation bran