A comparative study on the two different kinds of ultrasonic linear motors (ULM), standing and travelling wave types, is described. Analytical modeling using the wave theory and the contact mechanisms is presented. The former is used to describe the wave propagation in the stator, the latter to describe the interface between the slider and the stator, where the tangential and normal forces generated by the contact points allow the slider to describe a linear motion. FEM simulations allow to obtain transient and steady-state responses of the system and also to validate the analytical model. Harmonic analysis is also performed to find out the resonance frequency of the system and thus achieve a maximal amplitude response. In addition to these numerical analyses, some practical results on a standing wave linear motor are presented