Abstract: Flapping-wing Micro Air Vehicles (FMAV) are new conceptual air vehicles.They surpass the research fields of traditional airplane design and aerodynamics in relation to application technologies,and initiate the applications of MEMS technologies to aviation fields.The design,fabrication and dynamic characteristics of micro flapping actuator are the keys of FMAV designing.This paper studies a micro flapping mechanism based upon insect thorax and actuated by electrostatic force.Because there are strong nonlinear couplings between the two physical domains,electrical and mechanical,the dynamic characteristics of this system are very complicated.In this paper,the stable properties of equilibrium points are analyzed,the nonlinear dynamic characteristics of the system without damping and with damping are studied in the phase space,and the effects of original conditions and damping on the pull-in voltage are discussed.In addition,dynamic responses of the system to different voltage signals are analyzed.The results are helpful to the design,fabrication and application of the micro flapping actuator.