Based on design method for Turgo turbine structure, the optimal parameter combination was analyzed and selected by using orthogonal experiment design. An optimal turbine model was built and simulated numerically by using CFD technique to explore its performance, stability and efficiency at 500-900 r/min rotational speeds and 18-40 m3/h flow rates. In these flow rate and speed ranges, the optimal model has so high working efficiency that the best efficiency increases nearly up to 31%. The internal flow in the optimal model is more reasonable and smoother, and the uneven distribution of pressure in the inlet duct has been removed and an effective jet is formed as well. At the same time, the problem of local highpressure zone and the vortex between two blades disappear. Compared with the original model, the energy conversion efficiency of the runner was improved by 42.71%.