Three basic types of similarity relationship between the prototype and the model for dynamic structural model test and dynamic rupture model test are proposed in corresponding literatures. At the time the situation where various similarity relationships are applicable and the technique to ensure similarity for the different goals

to study dynamic behavior

elastic response and damage pattern

is discussed. The numerical simulation of model experiment of water-conveyance tunnel concerning fluid-structure interaction in soft soil is studied. Based on economic practicability of material selection for model test

the similarity relationship and the technique are proposed

which are validated through case study. The results of numerical simulation show that under the specific conditions

data of the model test can completely transfer to those of the prototype by using this type of similarity relationship

and getting more useful information. Some new ideas are introduced to keep the similarity of the hydraulic structures.