A　novel　Metal　Braided　Rubber-Silicone　Rubber　Composite　Seal　(MBR-SRCS)　is　proposed　for　extreme　conditions　(high/low　temperatures,　high　pressure).　Composite　seals,　fabricated　via　casting　molding　of　stainless　steel　wire　cores　with　varying　porosity　and　liquid　silicone　rubber,　were　optimized　(69.59　%　porosity,　15　%　compression　ratio)　through　compression　tests,　temperature　sealing　tests,　and　orthogonal　experiments.　The　optimized　seal　achieved　a　maximum　pressure　capacity　of　3.0　MPa　and　maintained　stable　sealing　from　218　K　to　473　K.　Stress　relaxation　tests　combined　with　an　Arrhenius　model　predicted　a　service　life　of　approximately　9.35　years　at　room　temperature,　significantly　outperforming　traditional　silicone　rubber　seals　(2.46　years).　Results　confirm　the　composite　structure　effectively　enhances　sealing　reliability　and　lifespan,　offering　critical　insights　for　engineering　high-performance　seals　under　extreme　conditions.