The transient process in the conduits of hydropower stations is a very complicated dynamic procedure coupled with fluid, machines, electricity, and even structure. The current methods used to analyze them separately cannot satisfy the design and the operation requirement of those large underground stations with long conduits. So it is necessary to develop a global physical simulation for the power station transients. As an initial discuss, this article focuses on the introduction of model similarity, model scale and some results about great fluctuation, small fluctuation and hydraulic interference in transient flow experiments.