The output power of the hydro-turbine is a key component in precisely modeling the stability characteristics of a hydro-turbine governing system (HTGS), especially in working conditions that is far away the optimum operating condition. In this study, first, we formulate the energy losses of HTGS's components to present the hydro-turbine's output power and utilize it to establish a novel mathematical model of HTGS. Second, we perform global sensitivity analysis to extract sensitive parameters of the conversion efficiency, optimize the values of model parameters based sensitive results, and verify HTGS model to be effective in different working conditions by experimental data. Third, the distribution characteristics of energy losses are investigated with the increasing guide vane, and the corresponding stability regions are presented to predict the characteristics of transient stability trend. The obtained results could contribute to the optimization analysis and control of HTGS in working conditions that is far away the optimum operating condition. (C) 2018 Elsevier Ltd. All rights reserved.