Due to the development of advanced manufacturing technology and the introduction of Smart-Manufacturing notion in the field of modern industrial production, welding flexible manufacturing system (WFMS) using robot technology has become the inevitable developing direction on welding automation. In WFMS process, the flexibility for different welding products and the realizing on corresponding welding parameters control are the guarantees for welding quality. Based on a new intelligent arc-welding flexible manufacturing cell (WFMC), the system structure and control policies are studied in this paper. Aiming at the different information flows among every subsystem and central monitoring computer in this WFMC, Petri net theory is introduced into the process of welding manufacturing. With its help, a discrete control model of WFMC has been constructed, in which the system status is regarded as place and the control process is regarded as transition. Moreover, grounded on automation Petri net principle, the judging and utilizing of information obtained from welding sensors are imported into net structure, which extends the traditional Petri net concepts. The control model and policies researched in this paper have established foundation for further intelligent real-time control on WFMC and WFMS.