Based on torsional dynamic theory,appropriate equations are developed that gain insight into the actuating voltage,switching time and other dynamic parameters for a micro-mirror using electrostatic actuation.The analytical results are discussed in detail without and with considering air squeeze film damping,respectively.It is equivalent to assume that the mirror is operated in vacuum or at ambient pressure.When the effect of the damping is considered,the movement trajectory of the cantilever beam is changed,and the calculated results of the pull-in voltage and switching time are considerably different compared with those without considering damping.Therefore,the effect of the air squeeze film damping is an important factor in the design and fabrication of micro-electro-mechanical systems(MEMS).Finally,an optical technique is described for the measurement of the deflection angle and switching time of the device.The experimental results are in agreement with the theoretical analysis.