An equivalent single layer model, as well as one-dimensional spring-mass-capacitor model, has been built up, to simplify the electrostatic analysis of multiple-layer fixed-fixed beam of 1.55 μm Si-based MOEMS tunable optical filters. The effects of the structure parameters of the beams, the electrode geometry and initial air gap to the tuning coefficient, have been analyzed. The tuning characteristics have been simulated quantitatively with the classical mechanical theory and transfer matrix methods. The simulations fit in well with the experimental results.