In view of the great influence of the distributor's hydraulic loss on the efficiency of the hydro-turbine，and plus the complexity of the hydraulic loss model，a method based on curve fitting is proposed to express the hydraulic loss of the distributor，and a detailed hydro-turbine model is developed.The improved artificial fish swarm algorithm（IAFSA）is used to identify the model.This method is applied to the data of a hydropower station.The simulation results show that the improved hydro-turbine model has a high accuracy and can reflect the actual running state.The identified results on the hydraulic loss of the distributor is identical to the theoretical formula analysis.The model is validated by the power step disturbance method，the results showing that it is reliable and accurate.