The utility model discloses a device for uniformly increasing the moisture content of materials. The device comprises a conveying mesh belt, an air temperature and humidity regulation device, a humidifying chamber body, a positive pressure air flow injection structure and a negative pressure system; the conveying mesh belt is used for conveying the materials; the air temperature and humidity in the humidifying chamber body can be stable and can be adjusted through the air temperature and humidity regulation device; the upper portion of the humidifying chamber body is provided with a plurality of groups of nozzles which are located above the conveying mesh belt; a plurality of spraying and blowing pipes which are arranged side by side and used for spraying and blowing the continuous positive pressure air flow are arranged in the humidifying chamber body and below the conveying mesh belt; every spraying and blowing pipe is provided with a slotted opening; the opening direction of every spraying and blowing opening is towards the conveying mesh belt; the negative pressure system is a hollow cover, wherein the upper end of the negative pressure system is in a square shape and the lower end of the negative pressure system is gradually changed into a circular shape; an internal center area of the hollow cover is provided with an upper and lower double-spherical hole plate combination structure which is fixed on the inner wall of an air suction cover through two wing-shaped structures.