In this paper an autonomous decentralized assembly system led by product part agent is proposed. Products such as parts, and sub-assembled parts are configured as agents in addition to devices in the proposed autonomous assembly system. Product parts for assembly are divided into two types. One is the main part that is the base of the assembled product and the other is for sub parts that are installed on the main part. The main part agent takes the initiative in this assembly system. The main part agent is dynamically created with the product model. The main part agent generates the process plan that contains the assembly sequence to complete the product, operations in each process and the required sub parts. The main part agent schedules the assembly operations by communicating with assembly machine agents and other main part agents. The autonomous assembly process was simulated using the implemented agents.