The invention belongs to the technical field of seawater desalination, and relates to a utilization device of the steam waste heat of a vacuum device of a low-temperature multi-effect distillation seawater desalination system, a system containing the device, and a utilization method of the steam waste heat. The steam waste heat utilization device comprises one and more steam ejectors and corresponding steam/liquid heat exchangers; by using the steam ejectors and using high-temperature and high-pressure steam as a power, the steam with a low temperature and a low pressure discharged by the vacuum device of the low-temperature multi-effect distillation seawater desalination system is ejected so as to increase the pressure and the temperature of the ejected steam; the steam generated by the steam ejectors enters into the corresponding steam/liquid heat exchangers, and exchanges heat with material water so as to increase the temperature of the charging water in an evaporator and allow thesteam to condense into fresh water. The device can effectively utilize low-grade steam, save energy, increase water generation ratio, and has important significance in the improvement of the economy of low-temperature multi-effect distillation seawater desalination systems.