This book introduces the research background and significance of carbon emissions in the tunnel industry and systematically reviewed the research progresses of carbon emission researches for tunnels, LCA (life cycle assessment) research framework, and uncertainty research progress. The authors propose a novel modular carbon emission calculation method for highway tunnel construction and expounds on the modular LCA system boundary theory of tunnel construction. This method does not require abundant knowledge of LCA modeling, which is convenient for general engineering and technical personnel to calculate the carbon emission level of tunnel construction. The calculation formulas for input and carbon emissions of each module are provided. It also analyzes the parameter uncertainty, model uncertainty, and scenario uncertainty of the carbon emissions from tunnel construction by the Monte Carlo method. Further, this book proposes the fitting model of carbon emissions of unit engineering quantity in tunnel construction, which benefits to simplify the calculation of carbon emissions. This book is mainly aimed at engineering and technical personnel in the construction industry, especially tunnel and underground engineering, including tunnel design engineers; tunnel construction engineers, experts, and scholars; tunnel owners; management departments.