A structure input and output method of graphic cells object oriented is proposed, and input and output model based on OpenGL graphic industry standard is founded. Using the technologies of MFC and OpenGL, the input, display and dynamic output of 3D graphics are realized, which are based on graphic cells such as node, beam, triangle, quadrangle element. Graphic cells keep consistency well with the elements of finite element in the aspects of geometry, reading and writing of structure files and so on. Using the model, the functions of structure input, data gathering and analyzing, and modal vibrating shapes output etc are finished. A visual experiment modal analysis system is daeloped.