Guigang ship lock for navigation of Xijiang river is very important,which locates in key position of the main navigation lines.A scaled model of emptying valve was established at Guigang second-line ship lock with length scale 1:15.The net opening and closing forces is systematically studied for three structural valves in six emergency valve closing situations.The influent of shapes of root edge of valve and face plate of valve on net opening and closing forces is obtained:1)The fluctuation of water level in downstream river will induce fluctuation of net lifting forces of valve because the water can flow into and out the well of valve freely when downstream face plate of valve was opened.2) The pressure of tilted panel of root edge is low and the suction force plays a main role at the root edge of valve when the tilted panel of root edge faces downstream.As a result,the net opening forces of valve with tilted panel of root edge facing downstream are bigger and net closing forces are smaller than those of valve with tilted panel of root edge facing upstream.3)The pressure of tilted panel of root edge is high and the lifting force plays a main role at the root edge of valve when the tilted panel of root edge faces upstream.Consequently,the net opening forces of valve with tilted panel of root edge facing upstream are lower and net closing forces are higher than those of valve with tilted panel of root edge facing downstream.An extra weight for valve should be considered when a valve with tilted panel of root edge facing upstream was applied.