Through the hydraulic model test, a more convenient and accurate method of deter- mining discharge coefficients in the sluice type of tide gates can be derived by the use of aubmergence ratio as a parameter. The results obtained are summarized as follows; 1. Discharge coefficients under submerged flow conditions can be obtained by the application of sutmergerice ratio (S) to the free flow equation of the broad-erested we r. 2. The critical submergence ratios (Scr) for the flat basin and the broad-crested types of sill have the same value of 0.8. 3. Under free flow conditions, the discharge coefficient (m) are 0.37 and 0. 35 for the flat basin and the broad-crested types of sill respectively. However, when submerged flow condition exists, the discharge coefficients for both types of sill is given by a regression equation of discharge coefficients (IL) on submergence ratios (8) expressed as; m 1.3- 1. 17S. 4. The relationships between S and Froude number (Fr), for the flat basin and the broad-crested types of sill are Fr=2. 79-2.495 and Fr2.5=5. 7-6.16S respectively. From the above relationships, it can be concluded that m can also be expressed in terms of the Froude number which is a very relevant hydraulic parameter of the open channel hydraulics.