To study the water-permeable characteristics and hydrodynamic characteristics of permeable structures, a specific physical flume model test with a PIV flow field measurement system combined with a Flow3D numerical simulation was used to study the water surface profile and permeable rate variation law of an open trapezoidal permeable submerged dam. The results show that the height of backwater and hydraulic drop near the submerged dam decreases with the increase of permeability, and a reverse slope phenomenon appears in the water surface behind the submerged dam with different permeability. Under the same cross-section average flow rate conditions, larger water depth corresponds to lower relative backwater height. When the water depth is greater than 2 times of the dam height, backwater gradually disappears. Under the condition of the same water depth in the far field in front of the dam, hydraulic drop height increases with the increase of cross-section average flow velocity. Finally, a comprehensive calculation formula of permeability is obtained by regression analysis of the numerical calculation results. It is proved that the maximum deviation between the empirical formula calculation results and the measured values is within 5%, showing a certain reliability.