The mistuning strength referred to as “small mistuning” was defined based on the frequency differences between the tuned and mistuned bladed disk. The existence and distribution of the small mistuning in industrial bladed disks were introduced. A lumped parameter bladed disk model with three-degree-of-freedom (3-DOF) in each sector was used as an example to investigate the effects of small mistuning on the dynamic characteristics. The results indicated that small mistuning can lead to severe vibration localization at the maximum nodal diameter. For the studied example

mistuning strength 0.001 can lead to a modal localization factor 17

and mistuning strength 0.007 can lead to a maximum amplitude amplification factor 1.8. Therefore

special attention must be paid to small mistuning during design and service stages of the bladed disk structures.