The　macro　modeling　method　for　Micro-electro-mechanical　System　(MEMS)　devices　is　a　key　issue　in　the　design　and　simulation　of　MEMS　system.　For　establishing　the　macro　model　of　the　nonlinear　silicon　diaphragm　drived　by　a　distributed　electrostatic　force,　a　nonlinear　function　fitting　scheme　was　used　to　calculate　the　energy　data　after　finite　element　analysis　for　establishing　an　analytical　model　of　kinetic　energy,　strain　energy　and　electrostatic　co-energy　of　the　system.　Then,　all　these　energy　functions　were　represented　in　the　term　of　general　mode　coordinates　and　were　subjected　into　the　Lagrange　equation　to　deduce　the　motion　equations　of　the　silicon　diaphragm.　Thus　a　macro　model　was　obtained　to　simulate　the　quasi-static　and　dynamic　characteristics　of　the　device.　By　comparing　the　macro　model　and　the　finite　element　calculating,　it　concludes　that　the　macro　model　can　capture　the　quasi-state　and　dynamic　behaviors　of　the　electrostatic　drive　device　quite　well.　And　this　modeling　method　can　consider　the　effects　of　residual　stress　and　nonlinear　geometry　and　can　reduce　lots　of　computational　cost.