Based on the Kirchhoff plate theory and the modified couple stress theory (MCST)，this work focuses on the pull-in phenomena of elastic micro-plates with damage. The dynamic governing equation of the micro-plate was derived and then solved via Galerkin method. The effect of damage variable，length scale parameter，initial gap and fringing filed on pull-in voltage of the micro-plate was discussed in detail. Moreover，the reliability of present model was validated by comparing results obtained in this study and the literatures. Numerical results show that damage effect decreases pull-in voltage while size effect increases it; large initial gap results in large pull-in voltage and fringing field has slight influence on it. This research is helpful and useful in electrostatically actuated microstructures applications and provides a theoretical foundation for designers and engineers.