The invention discloses a control system and a method of a heptefluoropropane fire-extinguishing device used for boats. The control system comprises a fire-extinguishing control device, a heat detector, a smoke detector, a light detector, a main power supply, a backup power supply, an emergency start/close button, a displayer, a control panel, an audible and visual alarm, a deflating indicator light, a device interlock, a fire-extinguishing starting device, a pressure signal transmitter, a heptefluoropropane storage bottle, a heptefluoropropane container valve electromagnetic starter, a relief valve electromagnetic starter, an emergency operating panel, a nitrogen storage bottle, a container valve of the nitrogen storage bottle, and the like. According to the system and the method, three fire-extinguishing starting manners, namely an automatic manner, a hand-operated manner and an emergency manner, are adopted, thus enhancing the reliability of the system and avoiding invalidation when the system is dealing with an emergency event. In addition, a fire-extinguishing starting device delay time adjustable technology is adopted. When the technology is applied in a matching manner, the delay time of the fire extinguishing starting device can be adjusted according to the practical situations of protection areas and sites, thus guaranteeing in-time safe evacuation of people in the protection areas and improving the application adaptability of the system.