Human joint is soft and flexible and has very important roles to play when human tries to walk, run or lift something. Many previous researchers have studied on the mechanics of human joint. In this paper, The dynamics of ankle joint can be expressed by a second-order linear differential equation constructed by inertial, viscosity and stiffness, these impedance parameters can be identified by system identification by testing the impulse response. the kinematic model of human ankle joint which takes flexible factors into account during walking and the method to identify the impedance parameters using snap-through buckling mechanism(snap motor), its design and available impulsive force are studied in this paper.