The hydro-floating shiplift is a new type of shiplift.Based on a hydro-floating shiplift project，we probe into the selection of filling and empting system valve and the characteristics of plunger valve.With a scaled 1:10.667 physical model，we research the flow coefficients，wall fluctuating pressure，critical cavitation number and cavitation form of the sudden enlargement and three-branch pipe，and explore the hydraulic priority of the sudden enlargement design for the flow passage behind valve.This study provides reference for the research and design of the valve section of hydro-floating shiplift filling and empting system.