AbstractIn this paper, cavitation in water hydraulic poppet valves is investigated by an experimental method with a half cut test model. The situation of cavitation appearance, the effects of cavitation on the characteristics of flow rate, noise level, pressure distributions and the boundary of inception of the cavitation are investigated. Comparison between a poppet valve with sharp edged seat and another, which has a length on the seat, is made. The effects of change in the shape of the seat are discussed as well as the effect of cavitation appearance. As a result, it is revealed that the sharp edged seat valve is less influenced by the cavitation on its characteristics.