This paper presents the dynamic characteristics of the piezoelectric inertia friction motors with the Coulomb and Karnopp friction models. Working principles and kinematics models of the motors with the friction drive mechanism and inertia drive mechanism are introduced. From numerical simulations, motion responses of the two types of motors with the two friction models are obtained. It is shown that the static frictional force plays an important role in the stick-slip working condition for the friction drive mechanism, which means the Karnopp model would be more acceptable. For the inertia drive mechanism, the results of two models are almost the same in the stick-slip and slip-slip conditions.