The extensive use of stiffened shells in aerospace industries is mainly motivated by the high stiffness-to-weight and strength-to-weight ratios.For these thin-walled structures, buckling is one of the main failure patterns.Several methods and programs are available for the analysis of stiffened shells, ranging from simple closed form solutions to complicated discrete solutions.Furthermore, many optimizations have been carried out for metallic and composite stiffened shells against buckling.The variables involved in the optimizations are usually stiffener size, stiffener spacing, skin laminate sequence and angle, etc.However, the layout optimizations of stiffened shells are rarely reported, which are capable of increasing the bending stiffness without the increase of structural weight.Actually, the buckling of stiffened shells can be categorized as elastic and plastic buckling patterns, and the failures mostly occur at the intermediate section of shell and the sections close to both ends respectively.It is supposed to be efficient to adjust the location of stiffeners for the purpose of improving the local stiffness against buckling, moreover, without the increase of additional weight.