According to the complex boundary condition of real bridge structure, appendix restraint parameters of structure boundary condition were detailed analyzed. The appendix horizontal and torsional restraint parameters were selected as research object. The least square constrained optimization inversion method was used to establish the question of reverse of bridge structure boundary appendix parameters based on tested and calculated mode parameters. The first order perturbation of eigen-value and eigen-vector based on matrix perturbation theory were substituted into the constrained optimization inversion equation, so the solving efficiency was improved greatly, and the iteration method was used to improve the precision. The corresponding program was made, and the example of a maglev railway girder shows that fairly well precise bridge structure boundary appendix parameters can be reserved with only former several modes parameters through four to seven times of iteration calculation.