Recently, there are growing interests in building LCCO2 Assessment to reduce carbon emissions. However, existing methods of assessment system include inefficiency in the process of CO2 calculation requiring considerable data input. Therefore, the purpose of this study is to develop an efficient building assessment system appropriate to material production in construction stage. To that end, quantity input technology was limited to data mapping. Also quantity calculation based on work breakdown structure and item codes consisted of hierarchical structure that is based on facet classification were analyzed. As a result, connectivity links of quantity calculation and CO2 functional units through item codes for data mapping, and assessment system including calculation and database parts were developed.