As revealed by Fukushima Daiichi nuclear disaster, countermeasures against severe accident in' nuclear power plants are an urgent need. In particular, from the viewpoint of protecting containment and suppressing the diffusion of radioactive materials, it is important to develop the device which allows filtered venting of contaminated high pressure gas. In the filtered venting system that used in European reactors, so called Venturi scrubbers are used to realize filtered venting without any power supply [1, 2]. The Venturi scrubber operates without a power supply of high pressure gas filled into the containment. In this apparatus, scrubbing of contaminated gas is promoted by both gas releases through a submerged Venturi tube which is one of the major components of Venturi scrubber and liquid splay flow formed by liquid suction through a hole for suction provided at the throat part of the Venturi tube. This type of Venturi scrubbers is called self-priming ones. The one of characteristics of the self-priming Venturi scrubber is that the liquid flow rate depends on the gas flow velocity. There is a potential to simplify that the liquid flow rate evaluation method because of the characteristic. In this study, our purpose is to reveal the relationship between the liquid flow rate and the hydraulic behavior in the self-priming venturi scrubber, and develop the liquid flow rate estimation method. In this paper, we conducted visualized observation and the measurement of the liquid flow rate experiment and weigh the liquid flow rate against the effects of hydraulic behavior. As a result, it is suggested that the increase and decrease of the liquid flow rate depends on the changes of the hydraulic behavior.