Vibroplatform test is an important method to study seismic performance of engineering structure.Processing the similarity relation and deducing response of original mold correctly are very important.Taking one four-story frame building as an example,this paperdiscussed the similarity relation of the original model and enough artificial mass and without enough artificial mass,and earthquake response of the original model and model were calculated by using finite element programe;response of original model according to response of the model was deduced;the calculation result from basic natural vibration period,acceleration,velocity,displacement and structural base shear were compared.Finally,the correctness of dynamic similitude law at the elastic stag was validated.