This paper discusses and suggests a basic structure of a mixed constitute of lightweight membranes and booms by looking slightly future of space structure which will become larger and larger to be tens of meter class such like future deep space exploration by solar sails or self-power generation by thin solar films etc⋯Or in short-sighted developing vision, this type of structure is going to be applied to the deorbit hardware for low-orbit satellites to earn much drag for atmosphere entry within smaller years. All of such application need that the structure should have a certain stiffness, so our interest is how to design to get efficient stiffness improvement and also we should be care not to ruin other structural merit such like small wrinkle amount. First, we focused on adding extension force in axial direction of each boom and studied where to put. Then the efficiency of cable connection on the oblique line of a membrane is also verified. After integrated these design factors, we focused on the actual construction phase that may be difficult to realize completely flat surface especially in tens of meters class structure, so we assumed that the manufactured structure will be steric, and we focused on finding the steric stabilized structure by using boom and cables as supportive members. Relation between 1st eigen frequency which is the bending mode of a boom is mainly studied and it becomes obvious that the steric structure improves it more efficiently than other design factor. These examinations are not only carried out on square model, but also on hexagonal model which is also versatile geometry for expanding module structure in the future, and this shows that the optimum boom angle exists to make wrinkle amount becomes minimum. This can be a designing guidepost for future use of boom-membrane structure. Then we consider all the design factor at once and suggest the three dimensional basic structural design for large light weight space structure.