This paper presents a new analytical method to simplify the analysis of hydraulic forces on the radial vibration of hydro-turbine generator units. The torsional effects of hydraulic forces exerted on the runner were considered in the new analytical method. The hydraulic forces calculated by the new analytical method were exerted on the runner node of a 125 MW Kaplan turbine unit rotordynamic model to investigate the numerical response of the unit with uneven runner blade opening and uneven guide vane opening. Meanwhile, the field data of vibration for the unit with load are examined for comparing with the numerical response. The new analytical method on simplifying hydraulic forces might be suitable according to the comparison between the numerical response and the field data analysis.