In this paper, a new approach to trajectory planning, performance Evaluation, and control for robotic assembly is presented. The assembly process is modeled as a discrete event system using synchronized Petri nets (SynPN). In a SynPN model, transitions are associated with firing conditions depending on external events. Due to this characteristic, SynPN is commonly used to model the connection between system states and external signals. The most important force/moment and position/orientation information in the assembly process serve as external events. Using the external events, the assembly states can be recognized and the system will be directed to the desired end state. Furthermore, trajectory planning algorithms and performance evaluation criteria of a discrete event system are also studied based on SynPN model. Finally, simulation and simple experiments are discussed in which a successful peg-in-hole assembly is fulfilled.