This paper proposes size and shape optimization of Tensegrity structures by using micro-genetic algorithm. Tensegrity structures are general pin-jointed systems of discontinuous compressive members(Struts) and continuous tensile members(Cables). Form-finding process has been done before performing optimization of Tensegrity structures. The micro-genetic algorithm are employed for efficient optimum design. The object function for size and shape optimization is weight in all design constraints. The design constraints include stress and strength constraints, and cables and struts are applied as different design constraints. A few Tensegrity structure example is shown to demonstrate the efficiency and robustness of the proposed method.