In this paper, a micro resonator is modeled as a thin rectangular microplate with ther- moelastic damping that is actuated electrostatically. Large static deformation due to high polarization voltage is considered, and vibration of microplate occurs around the static de- flection. Due to the effect of thermoelastic damping, the frequency of vibration is a complex value that is used to determine the quality factor of thermoelastic damping. Also, the pull-in voltage is considered because nonlinear properties are more appeared when approaching the polarization voltage to the pull-in voltage.