Batch processing process denotes the process used in the workflow management systems (WfMSs) supporting dynamic batch processing. During the run time of their concurrent process instances, multiple activity cases of the same type may be vertically combined together according to some batch logics and submitted for execution as a whole. Therefore, it is necessary to study the actual way process instances are executed. In this paper, we propose an algorithm to mine batch processing process from system logs. A case study is also done to illustrate its effectiveness.