The invention discloses a stress calculation method for no-linear flexible members without influence of external environmental factors. The stress calculation method comprises following steps of: firstly, generating stiffness matrixes, nodal displacement arrays and nodal load arrays of member units of an iron tower as for all member units and nodal displacement of the iron tower based on structural compositions of the iron tower, a structural model for material selection and a material model; secondly, correcting acquired stress matrixes and displacement matrixes employing a finite increment method and a Newton iteration method; and finally, acquiring loads and displacement of the overall iron tower in order to acquire stress magnitude of any point in the structure of the iron tower by performing lagrange's interpolation on stress matrixes and displacement matrixes of the iron tower. The stress calculation method for no-linear flexible members without influence of external environmental factors has following beneficial effects: effective calculations of stress for no-linear flexible members of a transmission line tower are directly made through a mathematical method, which provides an important scientific basis for safety evaluation of the structure of the iron tower.