The propeller shaft of the shafting system has various pattern by the engine power, propeller eccentric thrust and weight, which increases the adverse effect of bearing failure causing load variation on after stern tube bearing. To prevent this, diverse research on the shafting system has been conducted with a focus on optimize the relative slope angle and oil film thickness between the shaft and the support bearing, mainly based on the Rules for the Classification of Steel Ships. However, in order to secure the integrity of the shafting system through a more scrutinized assessment, it is necessary to consider the dynamic condition including the transient condition due to the sudden alteration in the stern wakefield. In this context, for the case ship, this study deals with the effect of propeller shaft behavior at rapid rudder turn portside, which is one of the typical transient conditions at ballast draught. As a result of the analysis, it was confirmed that the estimation of the change of the propulsion shaft behavior due to the transient condition have a different pattern from the interpretation in the quasi-static condition.