The performance of the sealing material in the electric equipment is prone to be reduced due to aging in the humid and hot environment

the resulting sealing failure will affect safe and stable operation of electrical equipment. For studying the aging characteristic of the sealing materials in humid and hot environment

the acrylonitrilebutadiene rubber（NBR）

fluororubber（FKM）and ethylene-propylene-diene monomer rubber（EPDM）

which are commonly used in oil seal and gas seal

are selected in this paper for humid and hot aging experiment. The changes of mechanical properties of the sealing materials during aging period are tested and analyzed

and the unaged as well as humid and hot aged sealing materials are analyzed by such tools as Fourier transform infrared

thermal analyzer and scanning electron microscope.It is concluded through the test that migration volatilization of the filler of NBR occurs in the humid and hot aging

while FKM and EPDM will absorb moisture and increase weight in humid and hot environment. It is shown by the variation in the permanent deformation of compression that FKM is easy to be affected by external stress and has large permanent deformation;The elongation at break of NBR and FKM after hydrothermal aging reduces significantly

while the EPDM shows stable mechanical properties;The three kinds of rubbers are mainly hydrolyzed and crosslinked in humid and hot aging

in which the chemical structure and components change of nitrile rubber are greatly affected by he humid and hot aging. The chemical structure

micro morphology and components of EPDM are most stable in the humid and hot aging and the resistance performance to the humid and hot aging is the best.