The invention discloses a negative-pressure ventilation and air exchange device for granary storage. The device comprises a base, a first pressure sensor and a single-chip microcomputer controller; athrough hole is formed in the center of the base, a central net-shaped air inlet pipe is fixedly welded to the upper end of the through hole, and a temperature and humidity sensor is arranged on the outer wall of the lower end of the central net-shaped air inlet pipe; the first pressure sensor is arranged at the upper end of a granary inner cavity, a second pressure sensor is arranged below the first pressure sensor, and an indicator lamp, a displayer and a touch sensing keyboard are arranged on the front end face of the base from top to bottom in sequence; an input end of the single-chip microcomputer controller is electrically connected with output ends of the temperature and humidity sensor, the first pressure sensor, the second pressure sensor, a capacitive sensing detection circuit and a power supply module separately, and an output end of the single-chip microcomputer controller is electrically connected with input ends of a fan, the indicator lamp and the displayer separately. According to the negative-pressure ventilation and air exchange device for granary storage, negative-pressure ventilation is adopted, damp air in a granary is discharged, and the grain quality is guaranteed.