The invention discloses a self-moving granary detecting device and a detecting method thereof, belongs to the field of granary grain mildew detecting equipment, and particularly relates to a detecting device which can move freely in a granary. The self-moving granary detecting device is characterized in that a detector and a guiding device are included, the detector is provided with an outer shell (3), the bottom of the outer shell (3) is connected with a transparent cover (1), the top of the outer shell (3) is connected with the guiding device, a circuit board (10) is fixedly arranged in the middle inside the detector, an image capture device and an internal environment detection device are mounted on one side, facing the transparent cover (1), of the circuit board (10), and a wireless transmitting device is mounted in the middle of the circuit board (10); one side of the outer portion of the guiding device is connected with a recovery device, and the recovery device is used for driving the detector to achieve self moving. By means of the self-moving granary detecting device and the detecting method thereof, image capture at any position inside the granary can be achieved, the device can move freely in grain heaps, and thus the grain mildew condition can be detected rapidly and accurately.