A grain storage system designed to vacuum package grain in a vacuum packaging bag, package the vacuum packaging bag containing grain in a waterproof bag and store the waterproof bag in seawater is provided to remarkably reduce storage costs. A grain storage system comprises: a vacuum packaging bag containing vacuum-packaged grain inside; a waterproof bag(10) in which a plurality of vacuum-packaged bags are received in the waterproof and packaged in a waterproof manner; a cable(30) to vertically connect the waterproof bag; a weight(40) connected to the lowermost waterproof bag of the waterproof bags; and a buoy(60) connected to the uppermost waterproof bag of the waterproof bags. The waterproof bag is formed with an air bag which is connected to an air pipe(50).
