The recurrent interaction patterns of information system usage within the post-implementation stage affect the realization of company researches in regard to the post-implementation stage are still very few. Therefore this research conducted a case study to explore the organizational routines of information system usage within post-implementation stage. An in-depth interview technique was applied to collect qualitative data, participants in information system post-implementation stage from three enterprises were interviewed Qualitative data was analyzed to reveal the contents and relationships of organizational. routines of information system usage, intervention practices and usage effect. The research result indicated that the organizational: routines of. information system usage are the interaction outcome of both standard operating procedures of information system and user effortful accomplishment. In addition, the relationships among information: system. organizational routines of Information system usage and user accomplishment reflect both feedback and feed forward organization learning and affect organization in various ways.