The　distance　of　air　gap　is　much　larger　than　the　mean　free　path　of　gas　molecules　for　MEMS　devices　with　small　vibration.　The　nonlinear　Reynolds　equation　can　be　transformed　into　linear　Reynolds　Eq.　based　on　this　condition　and　under　certain　assumptions.　Then　the　mathematical　model　of　damping　of　the　movable　armature　is　established　with　the　linear　Renault　equation.　The　damping　characteristics　of　the　movable　armature　are　studied　based　on　the　damping　force　mathematical　model.　The　relation　of　damping　coefficient　and　the　dimensions　of　movable　armature,　the　dimensions　of　air　gap　are　analyzed.　The　research　in　this　paper　provides　references　for　the　design　and　analysis　of　the　damping　coefficient　of　the　MEMS　devices　with　small　vibration.