Abstract: This paper makes research for the pivotal technology with the capacity expansion of turbine in FengTan Hydropower Station. Based on variation of water head and the shape of draft tube, it introduces the pivotal points of the hydraulic development of new turbine model and the acceptance test results. The hydraulic transition process of water transmission system after capacity expansion has been calculated and analyzed to ensure the safe and stable operation of the power station.The research results have guiding significance for the improvement of technology with capacity expansion of turbine in old hydropower plants in the future.