To solve the issue of modeling for loosely coupled inter-organizational workflows (LCIOWF), based on the colored Petri nets, the colored multi-dimension inter-organizational workflow (CMD/IOWF) Nets is proposed through importing color-set, colored function, resource places, waiting places, busy places, begin transitions, end transitions, roles, organizations, time functions, resource functions and transition functions into IOWF. Based on CMD/IOWF, the issue of modeling for multiple workflow instances in LCIOWF (loosely coupled inter-organizational workflow) coupling through resources sharing and activity synchronizing is discussed, as well as the issue of modeling for resources constraint and time relative to simulation. By means of defining inputs/outputs, states, events, time advancing functions and state transferring functions, a simulation model of loosely coupled inter-organizational workflows is presented. Based on the proposed simulation model, the key performance indexes of loosely coupled inter-organizational workflows can be obtained, which are the average execution time, the average execution cost of workflow instances of a respective project, their distributions among organizations and the resource-utilization ratio of a respective project. Finally, to verify validity of the proposed model, a case of loosely coupled inter-organizational workflows simulation is demonstrated.