The issue of deposited sediment diminishing reservoir efficiency has long been a concern for owners and operators of dams. Sediments may obstruct the dam's outlet, rendering the reservoir inactive. One technique for removing sediments from the dam is pressurized sediment flushing. The half-cone volume that is achieved by flushing sediment; this volume is dependent on a number of elements, including sediment properties, reservoir geometry, water level, and outlet flow. Nevertheless, it has been noted that pressure flushing removes a very little amount of sediment. The current study examined the effects of several effective factors on the volume of the sediment flushing half- cone in a laboratory setting. The tests included two water heights (0.90 and 0.70 meters), two sediment diameters (2.54 and 5.08 cm), two sediment heights above and below the discharge valve, three sediment slopes in varying states (0, 5, and 15%), and altering the initial slope distance from a to 0.5a. In total, 40 tests were conducted. Subsequently, the impact of each parameter checked out in relation to the experiment design, which included the response surface design technique and the ANOVA table. Finally, the numerical modeling using the Flow-3D program was examined. The results of the laboratory model and ANOVA analysis showed that the most effective in increasing the half-cone volume of sediment flushing includes the parameter of sediment height and discharge valve, by keeping other parameters constant and increasing the sediment height and discharge valve the volume of sediment flushing half-cone to the order was 8 and 6 , respectively. has been done, with the increase of water height and also the increase of slope and decrease of the initial distance of the start of the slope, the volume of the sediment flushing cone has increased. The sediment washing efficiency for water height (0.90 and 0.70) meters is very close to each other; but in general, lower water height has better efficiency, using Design Expert and SPSS software, a formula was obtained from laboratory results that had 93% accuracy. The numerical results that were done with Flow-3d software also had a good accuracy with the laboratory results and the results obtained from the formula.