The large amount of carbon dioxide (CO2) emissions from Chinese buildings has caused widespread concern among researchers around the world. A more comprehensive study is needed based on an international perspective as the standards and methods used for estimating emissions have not yet been integrated with international standards. It is necessary to quantify the life cycle emissions from reinforced concrete structures through a variety of actual engineering data and a multi-case empirical study to establish their standard value, in order to promote the rapid development of low-carbon buildings in China. Internationally, reinforced concrete structures are often grouped under six types: schools, hospitals, aerospace, commercial, residential, and prisons. This study examines residential, hospitals, commercial and schools as examples for multiple case studies. Life cycle cost analysis (LCA) principles, multi-case analysis and quantitative studies are combined to assemble a CO2 emission assessment model in SimaPro to evaluate the CO2 emission over the life cycle of a representative sample of reinforced concrete structures in China with the aim of developing proposals for energy-saving emission reductions. The results indicate that steel contributes 40%–53% to global warming and 40%–80% of the total environmental emissions during the construction phase of the buildings analyzed, with energy saving in the building materials production phase, especially steel production. The amount of CO2 emissions is generally 30% more in the use and maintenance phase than the construction phase, reaching even 300% for hospital buildings. By contrast, CO2 emissions during the demolition phase are relatively small, accounting for only 3%–12% of the building's life cycle. In terms of building type, the life-cycle CO2 emissions of hospital buildings are much larger than other types of reinforced concrete structures, reaching 3390 kg CO2 eq/m2.