Abstract: When pipe flow test device is used to simulate the industrial pipeline, similarity theorem is always applied to determine test model. A comparison on similarity theorem and principle of equal effective equivalent shear stress is carried out. Results demonstrate that it is irrational to determine flow rate of test device by the similarity theorem when wall changes, while the principle of equal effective equivalent shear stress can ensure the conformity of pipe flow state with actual industrial pipeline, which verity the rationality of principle of equal effective equivalent shear stress.