<p>Under the intermittent impact load during the high-efficiency milling of titanium alloy, the morphology of the residual machining transition surface changes dynamically. This variation directly affects the distribution of machined surface morphology and the fatigue performance of aviation components. Existed researches focused on addressing the overall deviation level of machined surface morphology from the design target; however, it overlooks the effects of instantaneous cutting behavior on the morphology distribution of the residual machining transition surface. Consequently, the time–frequency variability of machined surface morphology remains to be revealed. This study investigated the effects of cutter tooth errors and milling vibration on the instantaneous cutting contact relationship. A dynamic distribution model for the morphology of the residual machined transition surface was developed, and the time–frequency analysis method for the protrution height of the residual transition surface was selected to characterize the dynamic time–space distribution of machined surface morphology. The effects of milling vibration, cutter tooth errors, and process variables on machined surface morphology were revealed. An identification method for time–frequency variability of machined surface morphology was proposed and verified by experiments. The results showed that the calculated dynamic distribution of machined surface morphology are highly consistent with the experimental results. The proposed method could clarify the formation mechanism of machined surface morphology under milling vibration and instantaneous milling cutter position deviations.</p>