The invention relates to the technical field of steam-assisted gravity drainage (SAGD) production liquid treatment, and relates to a high-temperature closed dehydration device and a method for treating SAGD production liquid. The former comprises a high-temperature steam-carrying super-heavy oil slug flow capturing and treatment integrated device, a super-heavy oil high-temperature and high-efficiency elevation pre-dehydration device, a dehydrator, a pressure degreaser, a first heat exchanger, a second heat exchanger, a third heat exchanger, and a fourth heat exchanger. The high-temperature closed dehydration device and the method for treating the SAGD production liquid provided by the invention are not only suitable for the treatment of the SAGD production liquid, but also utilize wellhead back pressure to realize non-power operation, and can fully recycle thermal energy and reduce thermal energy loss. When the SAGD production liquid is treated by the method provided by the invention,the method provided by the invention has shorter dehydration time, smaller dosage and better oil delivery indexes than the existing conventional dehydration process. In addition, compared with foreign dehydration technologies, the method can deal with heavy oil with a higher difficulty coefficient, and the dosage is less.