The pursuit of sustainability is fundamentally impacting the way companies develop new products across the world. Life cycle design (LCD) is believed to be a promising approach to the realization of a sustainable production and consumption system. Within the methodology framework of LCD, comprehensive and systematic considerations of different aspects (e.g., product, process, service) of the product development are required, as well as the holistic optimization of the whole life cycle (i.e., close the loop). Thus, cross-organizational collaboration is believed to be essential, but challenging for LCD. Conflict in collaboration is a key factor hindering the effective implementation of product lifecycle design: the differences in corporate strategy, interest demands, and technological level among stakeholders involved in product life cycle design, as well as the special “competition-cooperation” relationship between them, result in many obstacles in LCD collaborations. The introduction of environmentally friendly product attributes can disrupt the optimized balancing of existing product system functionality, performance, and cost, leading to conflicts between new and existing attributes. This study aims to develop a knowledge repository for conflict management in LCD collaboration and to facilitate collaborative eco-design practices of complex mechatronic product (i.e., manufacturing equipment, construction machinery, vehicles). An ontology-based representation of conflict typology and conflict-resolving process in life cycle design collaborations are first proposed, which enable the structuring and standardization of related data, the storage of such data in a computer-processable manner, and generation of conflict management case knowledge. Descriptive features of conflict management case are defined in accordance to the ontology model, based on which the similarity between case and case queries is calculated using the nearest neighbor method and case retrieval is realized based on the calculated similarity. With the proposed ontology model, a cloud-based and micro-service architectured conflict-managing knowledge repository system prototype is then developed, which provide the benefits of low-cost deployment, better accessibility and easy maintenance.