Taking a typical structure of a friction-drive-type Linear motor with piezoelectric stacks for example, the drive principle of vibration friction is in vestigated. Based on the vibration detachment model of the motor system, the me chanics conditions of detachment between stator and slider are analyzed. Further,the influence of the construction parameters and operation parameters are analyzed on elliptical motion and vibration detachment. The prototype is investigated by experiments. It is shown that the exciting voltage and exciting frequency of piezoelectric stacks and the pre-pressure of motor have significant effects on vibration detachment.