Development of control model and system for AMS (Automated Manufacturing Systems) has long been interested by researchers. Presented in the paper is a systematic approach to constructing a Petri-nets(PNs) model of AMS and method for design a graphical model of a AMS by using a new modeling tool which is called PNs. So, the procedure of modeling in the AMS is the same as current practice of AMS design and is based on the IOM (Integrated Object-oriented Modeling) paradigm. An AMS, which consists of various machine groups, can produce machine parts in different physical dimensions and lot size. To model such a system, the method which utilizes Sub-PNs are proposed. This enables the models according to part routings. The machine group which causes bottleneck is obtained and modified to relieve the problem. By iterating these steps which consist of modelling, simulation, and performance evaluation, an AMS can e obtained which satisfies the required manufacturing conditions. Finally, the implementation issues of PN modeling are addressed. The approach is the IOM from PN modeling by Sub-PNs and the other is a development of IOM tool for the performance evaluation of AMS.