Abstract: Some experiments for the periodical leakage flow of small hole are performed. It is found that the forming of periodical leakage flow of small hole is not only related to the concentration, viscosity and compatibility of the liquid in the inner and exterior vessel, but also related to the crevice between the inner and exterior vessel. The change of the period is not only related to the density of the liquid in the inner and exterior vessel and the diameter of little hole, but also related to the diameter of the inner and exterior vessel.

Key words: periodicity, diameter of hole, compatibility, density