An　electromagnetic　microrelay　is　dynamically　designed　with　contact,　and　its　performance　principle　is　presented.　By　analysis　of　the　electromagnetic　driving　force　and　damp　force,　the　dynamic　model　is　established.　Synthetically　taken　into　account　the　dynamic　factors　of　inertia,　air　damping　and　contact　force,　the　armature＇s　pull-in　characteristic　is　discussed　in　detail.　The　analytical　results　indicate　that　structure　parameters　of　the　armature,　such　as　thickness,　width,　skin　and　thigh,　have　considerable　effect　on　the　contact　area,　switching　time　and　intensity　of　the　microrelay.　The　conclusions　of　this　paper　also　are　suitable　for　other　similar　microrelay.