Cable structures which are a kind of lightweight soft structural system are used for spatial structures with wide span. The material property of the cable has strong axial stiffness but little bending stiffness. So cable structures are unstable structures initially. These soft structures need introducing initial stresses first because of its initial unstable state, and it happens large displacement phenomenon. To find the structural shape after large displacement cause by introducing initial stiffness, we need the shape analysis considering geometric nonlinearity in structural design procedure. In this study, we will derive the nonlinear finite element formula for cable members considering geometric nonlinearity, and develope a computer program for the shape analysis using the tangent geometric equations. Results of some numerical studies are showing the developed analytic program is reliable.