It is desired that time constraints of a workflow model can be measured by more than one granularities for distributed processes. Aiming at the multi-granularity time constraints problems, a workflow model, MG-TWF, is proposed. By the definition of multi-granularity relative time constraints, multi-granularity absolute time constraints and multi-granularity time constraints workflow networks, multi-granularity time constraints of MG-TWF are described from MG-TWFs static building stage, dynamic running stage and workflow networks structure. In addition, consistency analysis methods of multi-granularity relative time constraints, multi-granularity absolute time constraints and multi-granularity time constraints workflow networks are developed. Finally presented a case study is presented using the consistency analysis methods of MG-TWF.