Abstract: The deployable antenna has been applied widely with development of space science and technology. Recently, the cable net structure becomes more and more popularized for it is not only with light weight and little furl volume, but also able to be made in large size. Considering the flexible cable net deployable antenna, the structural characteristics of the large deployed antenna for satellite have been discussed. And an optimum design model searching for minimum weight （volume）, considering both the size variables and prestress variables is studied. The reflect precision, eigenfrequency, strength and cable’s allowable stress is taken into account in the optimal design. The improved GA method is used to solve it with reasonable results.