Abstract: A modeling method was given to introduce detuning into finite element(FE) model based on a typical bladed disk assembly,in which random machining errors were considered as well.A modal localization factor was defined based on the blade strain energy,which assessed quantitatively the behavior of mode localization.ANSYS program and Monte Carlo simulations were performed with regard to the subjects of statistical characteristics of natural frequencies and mode shape.Results indicates that the detuning in blade design can increase the modal localization of bladed disk assemblies significantly,which requires consideration of the both aspects of vibration localization and aeroelastic stability for detuning design of bladed disk assemblies.