OKMD (Ontology-based Knowledge Management process for DMAIC) model is an integrated conceptual model that combines activities of DMAIC process, knowledge management and ontology engineering. The ultimate goal of OKMD model is to construct a knowledge base to accumulate and share knowledge created by DMAIC improvement process. Knowledge available should be represented by existing Ontologies. Thereby, knowledge resource of DMAIC improvement process will be preserved and reused sustainably.