Tensegrity mechanisms are new type mechanism consist of a set of compressive components (rigid rods) and continuous tensile components (ties). The benefits of tensegrity mechanisms in comparison with conventional ones include low mass, small inertia force, good flexibility and foldable. According to configuration principle of tensegrity structure, a 4-SPS type tensegrity mechanism under actuated was designed, which consist of a top platform, a base one and 4 elastic chains (springs) and 4 rigid driven chains (prismatic actuators). The vector equations were deduced from position relation of the mechanism, and the static equilibrium equation also was obtained include the quality of the rigid components. Due to the existence of unconstrained degree of freedom of the mechanism under actuated, analysis of this type of mechanism was more challenging and complicated in comparison with conventional mechanism. Positional positive and negative solution were analyzed through simultaneous minimum potential energy equation and position equation, and the numerical solutions of which also were acquired by using vriable step search method. Finally, velocity and acceleration equations of the mechanism were deduced under the condition of equilibrium, also, motion graphs are drew according to the equations.
