With　regards　to　the　mechanical　environment　not　meeting　operational　requirements,　several　steps　are　taken　to　address　the　issue　of　local　amplification　of　vibrations　in　individual　instruments　caused　by　secondary　isolation.　Firstly,　regarding　the　metal　rubber　double-layer　isolation　system,　the　flexible　stiffness　of　the　mounting　plate　is　fully　considered,　and　a　secondary　vibration　reduction　system　model　with　both　flexibility　and　rigidity　is　established.　Secondly,　based　on　the　target　frequency,　the　frequency　response　function　of　the　secondary　vibration　reduction　system　is　decoupled　systematically　to　solve　for　the　stiffness　of　the　damper.　Finite　element　analysis　is　then　employed　for　random　vibration　analysis　to　validate　the　feasibility　of　the　theory　model　of　the　composite　secondary　isolation　system.　Finally,　the　experimental　verification　is　conducted　using　a　vibration　table.　The　results　indicate　that　when　the　secondary　isolation　system　meets　the　engineering　stiffness　requirements　and　its　first　natural　frequency　is　below　40　Hz,　the　vibration　reduction　efficiency　can　reach　over　70%.　Experimental　results　are　generally　consistent　with　the　simulation　results.　©　2024　Nanjing　University　of　Aeronautics　an　Astronautics.　All　rights　reserved.