The static and dynamic similarity theories of structure experimentation model are presented by combining the equation analysis with dimension matrix analysis. The similar relationships between static and dynamic models，ratio of similitude，and similarity criteria of Dongtinghu three-tower cable-stayed Bridge in Yueyang City are deduced. The self-oscillating character and the dynamical response under the action of seismic wage of the prototype and the model are compared and analyzed based on finite element technique. By numerical analysis，the results of rigidity similitude model are deduced. As reasonable additional mass upon the model structure，the dynamical capability and dynamical response of the prototype meeting the requirement of engineering precision can be gained. For the additional mass question of large cable-stayed bridge model，the dynamical capability and the response of the bridge¢s tower and cable with or without additional mass under the action of three-dimensional earthquake wave are analyzed and compared. It shows that the structure design of model bridge satisfied primarily rigidity similitude. According to the similitude ratio and similitude criterion，the test results can be modified by the additional mass. It can provide references to the design and dynamical examination of structure.