The invention relates to a high-temperature comprehensive property evaluation experimental device of a sealing spacer, comprising a spacer loading system, a flange lifting separation system, a spacerdeformation measuring system, a heating and temperature control measuring system, a cooling heat insulation system, a medium setting system, a medium sealing and leakage rate measuring system and a data acquisition system. The invention has the advantages of high parameter, convenient experiment, compact structure of a whole experimental machine, small occupying area, and the like, takes a low-pressure area as a leakage measuring cavity, enhances the measuring precision of the pressure of the leakage measuring cavity and also effectively avoids the problem of pipeline leakage caused by takinga high-pressure area as a leakage cavity so that the measurement of the sealing property of the spacer is more accurate; and in addition, the flange lifting separation system can solve the problem ofthe difficult bonding and separation of the high-temperature experimental spacer and a flange.