The construction industry is one of the three largest carbon emitting industries in the world, accounting for up to thirty percent of global greenhouse gas emissions each year. Since traditional cast-in-situ building operations significantly contribute to these emissions and cannot therefore meet green building requirements, prefabricated buildings have come in to their own as a construction method that effectively reduces carbon emissions. Although studies have been conducted in to reducing carbon emissions by using prefabricated techniques at the building construction stage, none have focused on the reduction of carbon emissions by using prefabricated instead of cast-in-situ decoration systems. This study therefore used a case study in China to evaluate the carbon reduction potential of prefabricated decoration floor systems compared with traditional cast-in-situ decoration floor systems, and to also consider the carbon reduction pathways of four different types of prefabricated floor system from the perspectives of work methods and materials. Since the case study results showed that the carbon emissions reduction of the prefabricated floor system was 69.7%, or 101.5 kg CO2e per cubic meter, it can be concluded that there is a significant carbon reduction potential for using a prefabricated decoration floor system compared with a traditional cast-in-situ decoration floor system. The key contribution of the study is that it provides valuable references for interior decoration practitioners and decision makers when considering ways to reduce carbon emissions through prefabricated decoration floor systems.