The work aims to sign flexible contracts with suppliers to ensure that the military can get relief supplies quickly, efficiently and economically in response to emergency disasters, with respect to the supplier selection problem of emergency supplies. By establishing the random planning model, the supplier with the lowest procurement cost could be selected according to the agreement terms provided by different suppliers. This model could be used to analyze the contents that military procurement departments in areas prone to Ⅰ, Ⅱ, Ⅲ and Ⅳ grade disasters should focus on during negotiation when selecting emergency supplies suppliers. The flexible contract signed between the military procurement department and the emergency supplies supplier can reduce the total procurement cost as much as possible on the premise of ensuring the supply of supplies, thus achieving a win-win situation for both parties.