In this study, BUG 1 navigation algorithm which is a simple motion planner, is modelled by the Petri net (PN) for a mobile robot (MR). We prefer this PN model to obtain the discrete data for this algorithm. PN is used as a modelling formalism to define MR's movements such that the step of BUG 1 is constructed by using PN. Thus, all states are obtained the coverability tree. After all coverable marking vectors, the process of PN for BUG 1 is shown step by step on a real MR using the simulation environment of MobileSim.