To minimize structural mass of wrap around fins of the rocket under particular aerodynamic load, the structure optimal design of wrap around fins was done. The optimization took minimum structure mass as objective, some geometry parameters of the wrap around fins including fin length, thickness, leading edge sweepback and so on were chosen as the design variables, its intensity and distortion as the restrictions. Through integrating iSIGHT and MSC.PATRAN/NASTRAN, the optimization of the wrap around fins was done and preferable result was achieved, whose weight reduction was obvious. Then the optimization result was analyzed. It's found that the most influential design variables to optimal target and restrictions are central angle of wrap-around fins and the thickness.