Micro-hydro power is considered as one of the most abundant sources of electrical energy throughout the world. It is renewable, environmentally friendly and less expensive which can be used for vulnerable communities in the rural areas. The vast majority of the rural population in developing countries does not have access to electricity; they use kerosene which has a direct impact on the health of the people. Those challenges can be reduced by using renewable energy technologies like micro-hydro power to electrify the off-grid rural areas. Screw turbine is a potential machine element for the efficient generation of electricity at low head sites, in run-river and irrigation systems. Nowadays, screw turbine is under extensive investigation by using different approaches to determine various effects of parameters on the power output as well as on the efficiency but there is no optimum design that increases the power output and efficiency of a screw turbine. The aim of this research is design and optimization of screw turbine for the purpose of increasing the power output and efficiency by using theoretical analysis, ANSYS Workbench CFD, and response surface methodology. Through the use of computational fluid dynamics (CFD), a variety of screw turbine parameter which can affect the overall performance of the device were evaluated and investigated to get optimized geometric parameters such parameter is pitch of screw turbine, inner diameter of screw turbine and number of screw blade. and also, the research investigated the performance of a turbine for arrange of flow rates 0.01m 3 /s, 0.015m 3 /s and 0.02m 3 /s at the head difference between 0.5m and1m.The optimum designs increased the volume of flow in each screw bucket and decreased the surface area of the turbine in contact with the flow resulting the best performance. Keywords: Micro-hydro power; optimal design; CFD; Response surface methodology