Focused　on　3-dimensional　seismic　isolation　for　latticed　roofs,　the　mechanism　and　device　in　vertical　direction　of　the　bearing　are　discussed.　Firstly,　absolute　isolation　effectiveness　(Sie)　is　introduced.　Based　on　Sie,　the　relationship　between　vertical　stiffness　and　characteristic　frequency　of　input　excitations　is　established,　and　it　verifies　that　means　of　seismic　isolation　in　vertical　direction　is　realizable.　Then　the　formula　for　stiffness　in　vertical　direction　is　developed.　Finally,　some　parameters　related　to　the　design　of　springs　are　analyzed,　and　the　practical　measures　are　established　as　well.