The dynamic response of continuous box girder bridge when vehicle crossing was analyzed with a finite element calculation program. But the pre-post processing interface and graphic function are weak. In view of this, a mixed programming method was proposed by Fortran language with powerful computing function combined with Visual Basic language which has the good functions of visualization design. A finite element system for the calculation of bridge dynamic responseis worked out. This software not only can solve the complex engineering problems, but also has a good interactive interface. Some knotty problems encountered in the development process about mixed programming are described, and some corresponding solutions are given.