Abstract: Continuous transverse grates are commonly used in some urban or impervious areas to collect the runoff (the entrance of parking lots, under-crossing tunnels, and airport aprons), where it is hard to place conventional inlets due to lack of suitable transverse slopes or steep longitudinal slopes. Hydraulic efficiency of continuous transverse grates determines the flow rate into the underground sewer system during rainfall and is of great significance to preventing the occurrence of urban waterlogging. Eight types of continuous transverse grates commonly used in China were experimentally tested in this study with different approach flows (Q=10~80 m³/h) and a set of longitudinal slopes (S_L=1%~4%). A full-scale physical model simulating a 12 m long, 3 m wide road was constructed in the hydraulic lab in Hefei University of Technology for the hydraulic tests. Hydraulic efficiencies of these grates under different conditions were calculated during the tests, and their influencing factors were analyzed, including hydraulic parameters of the approaching flow (Froude number) and the geometric parameters of the grates (total area, length of the opening in flow direction, opening style and opening rate). The experimental results show that the hydraulic efficiency of different continuous transverse grates may not have a consistent relationship with the Froude number. The length of opening in flow direction may have greater influences on the efficiency than the opening area or rate. Compared to grates with rectangular openings symmetrically arranged, when the opening area and rate are the same, the grates with circular openings staggerly arranged are found to perform better for capturing runoff. Based on the Manning Equation and the orifice outflow formula, a set of empirical equations were also presented to relate the hydraulic efficiency and influencing factors. Good agreements were obtained between the predicted and measured results with relative difference of less than 15%.