We study a behavior of deformation of a composite that is reinforced along three mutually orthogonal axes under large deformations of tension. We use an applied variant of theory for performing macro-mechanical analysis of composite materials with the accuracy sufficient for practice. We consider a composite having small volume content of reinforcing fibers. It is noted that the properties of composites reinforced in three orthogonal directions under large deformations differ qualitatively from composites under small deformations. In the case of large deformations, there may occur a macroscopic loss of stability of the composites under considerations contrary to the case of three-dimensional composites having large volume content of reinforcing fibers.