Dynamic rescheduling decision-making problem is an important issue in modern manufacturing system with the feature of combinational computation complexity. This paper introduces a multi-agent based approach using the detailed process, provided by Prometheus methodology, which used for the design of a simultaneous dynamic rescheduling decision making for flexible flow line manufacturing system that working under dynamic customer demand. The application has been completely modeled with the Prometheus Design Tool (PDT), which offers full support to Prometheus Methodology. The proposed dynamic scheduling decision making system is developed for Automated UPVC door and Windows Company and can be support both static and dynamic scheduling.