Aiming at the problem that the migrating strategies of process instances are difficult to determine in process evolution

a workflow process model with flexible expressiveness was proposed

and the change of it is transformed into some change domains which contain three kinds of meta-change operations. In order to determine whether a process instances can be migrated to a new process model smoothly

an approach to find out all points of change(PoC)through confining the change domains was also proposed. The positions of PoCs were compared to the current states of process instances in order to decide the strategies of process evolution

and the process evolution algorithm was given and the migration of process instances was realized. The practical applications show that the proposed algorithm can deduce the process evolution strategies of workflow automatically

and the process instances migration can be carried out in batches.