Abstract: Timing constraint is a key factor in workflow model for distributed enterprises Based on TWF net,a new time workflow model,extended time workflow net（XTWF net ）,is proposed It aims to get over the deficiencies of time workflow net（TWF net） in modeling timing constraints for distributed enterprises By building rules,several TWF nets can form an XTWF net to characterize the timing constraint of parallel workflows;By introducing time mapping function with relation to time zones, XTWF net can characterize workflows distributed in multi time zones And finally presented is a case study using the XTWF net model