To　obtain　the　optimal　design　satisfying　strength　constraints　of　combined　structures　which　is　composed　of　truss,　beam,　shell　and　membrane　elements,　according　to　fully　stressed　criterion　and　using　dimension-less　design　variables,　the　approximate　explicit　optimization　model　of　combined　structure　is　founded　which　is　subjected　to　strength　constraints　and　size　constraints.　Taking　MSC/Patran　software　as　developing　platform　and　MSC/Nastran　software　as　finite　elements　analysis　tool,　the　sectional　area　optimization　program　is　coded　by　PCL　(Patran　Command　Language).　Numerical　examples　show　rationality　of　the　model　and　efficiency　of　the　program.