The research based on the production scheduling process of mechanical products in the workshop, established the Petri nets model process of production scheduling process of mechanical products, and then established the basic concepts of reliability in the production scheduling process of mechanical products. According to its function structure model, put forward the calculation model of reliability and its mathematical expressions in the production scheduling process of mechanical products. Finally the application example was given. This method provides a new research approach for the system stability evaluation and control in workshop production scheduling, has important value of application.