Rotary drilling rig is a kind of construction machinery which is used for deep pile foundation hole drilling operation. In recent years, a significant amount of catastrophic plastic-hinge type bending failures have occurred in the masks of the drilling machines. The major cause leading to this disaster is due to the sudden breaking of the drilling pipe lifting wire rope. The drilling rig will experience a severe transient dynamic process immediately after the accidental breaking of the lifting wire rope. The current design routine for drilling rigs is normally based on static analyses only, and the dynamic processes have seldom been considered due to the complexity involved in the analyses. In this paper, parametric finite element model for the entire machine of the rotary drilling rig has been established. Transient dynamic analyses have been carried out in response to the load case that the wire rope for drilling pipe lifting breaks. The history of stress variation over the whole machine during the dynamic response process has been obtained. This could be used to check if the machine designed is safe in case the drilling pipe lifting wire rope breaks.