Abstract: The article discusses the development and operation of the flexible manufacture system (FMS) computing design tool architecture with the Petri net.A comparative analysis of the existing problem, the main research problem is the implementation of intellectual simulation of the process of designing a flexible manufacture system and modeling of project work performed in its stages, which belongs to the class of complex technical systems.The aim of the work is to describe the activities of the FMS designed at the subject level with the use of Petri net modeling.At the initial stage of the design process, a generalized structure of the interconnections of the subsystems of the automated design tool was proposed to create and manage the information support of the design process of the FMS, working on the principle of flexible management.The issue of selection of the project object, arrangement, effective placement based on its active functions, organization of knowledge base on the basis of implicative elements, symbols and descriptive structure of natural language for modeling of imitation of technological operations was considered and resolved.The article shows that the most efficient and reliable modeling device in the system design phase is a universal and reliable Petri net device, which can be explained by the fact that the Petri network allows to study the feasibility of its creation without direct physical contact with the object.At the same time, it has been shown that Petri net are not considered efficient in modeling and researching relatively simple processes, and that the use of other modeling devices for their intended purpose is more efficient.It was noted that there are many extensions of Petri net and that they have been developed as effective software packages for modeling and researching FMS and are widely used in design procedures, especially in the study of FMS management, control, forecasting and other activities.The configuration scheme of the mechanical assembly line was selected as the object of research.The FMS module has a kinematic scheme of a crane-manipulator performing service technological functions in a threedimensional coordinate system (XYZ) so that by analyzing it, it is possible to accurately determine the generalized coordinates, velocity and acceleration and program it in the next stage.The problem of describing the sequential maintenance operations of lathes, milling, radial drills and bending machines in the mechanical assembly production module with the transition procedures and defining the information-measuring and control functions of the FMS was solved.Taking into account the sequence of activities of the research object, the management algorithm of each of its components is selected from the knowledge base at the predment level and transformed into the Petri network with the appropriate Petri net conversion algorithm and a systematic knowledge environment of information provision at the mathematical level is created.