in this paper, we've experimentally and theoretically (analytical and numerical) investigated the water jet pump. The effect of operational and geometrical parameters on the water jet pump efficiency was determined experimentally and theoretically. The experimental investigation was held `firstly to work out the effect of driving nozzle spacing, area ratio, diffuser angle, and throat length on the performance of water jet pump. The test rig has been designed to examine the jet pump's various parts using different dimensions and shapes. A MAT LAB computer program has been designed to support the derived formula and theoretical loss factors for all parts of the jet pump. the consequences of adjusting area ratio on the performance of the jet pump are investigated employing a Computational Fluid Dynamic (CFD) analysis with ANSYS FLUENT software The CFD analysis reveals that changing jet pump performance are often achieved by changing jet pump area ratio. The experimental results are compared with the analytical investigation and therefore the comparison indicates an honest agreement between them