Based on the data of China's prefecture-level city statistical yearbooks and environmental yearbooks from 2003 to 2018, the energy-saving and emission reduction effects of China's e-commerce model city construction are analysed using the multi-period double-difference method. It is found that the construction of national e-commerce model cities significantly reduces environmental pollution and energy consumption and significantly improves the structure of energy consumption, and that this effect is influenced by factors such as the level of marketisation, the degree of environmental regulation and the degree of informatisation. The estimation results of the mediated effect model show that the construction of national e-commerce demonstration cities promotes energy conservation and emission reduction mainly through the channel of industrial structure transformation and upgrading. The relevant policy implication is that the establishment of national e-commerce model cities is another important way to promote energy conservation and emission reduction, which helps to improve the quality of the ecological environment, reduce environmental risks, improve the level of ecological civilisation and develop a green economy.