OFF(Object File Format) is a kind of common format for three-dimensional model described with triangular mesh. The research of OFF is the foundation condition for reading, displaying and other operations. Nowadays, it doesn't have a set of standards and specifications about the simple analysis of OFF. First of all, the software is based on Visual C++6.0 developing platform and uses MFC to achieve a visual interface. In addition, we can read and write the OFF file taking advantage of C++ standard I/O library and the view of OFF file is implemented by using OpenGL technology. In the end, we have a system that realizes the functions of reading and displaying for OFF file while it completes the transformation of file from OFF to STL with format conversion algorithms.