It is extremely time and cost-consuming to carry out a full life cycle assessment(LCA) for a multi-component system like an automobile, since it consists of several thousands of components. In addition, the strictly limited time allowance in the planning stage of product development necessitates a practical methodology which. while adhering to the principles of LCA, provides useful life cycle inventory for a multi-component system within a much shorter period of time. Therefore, a practical methodology which consuming much shorter period of time and cost is needed. The purpose of this paper is to introduce a practical, systematic LCA methodology for a multi-component system by using module, with which a time and cost effective calculation can be ensured for a multi-component system.