An online carbon emission accounting method based on B/S structure for coal mines owned by the Coal Industry Group is proposed. Firstly, the carbon emission accounting method for coal mines owned by the Coal Industry Group is expounded, which is the basis of carbon emission accounting for coal mines. Secondly, an online accounting path of carbon emission for coal mines owned by the Coal Industry Group is proposed: The traditional top-down standalone accounting process of "carbon emission data acquisition, carbon emission calculation, carbon emission publication" is replaced by the bottom-up online accounting process of "carbon emission accounting tasks assignment, carbon emission data submission, carbon emission data audit, carbon emission calculation, carbon emission view", and the manual table lookup is replaced by system automatic table lookup to realize online calculation of carbon emissions. Then, taking Sql server as the database management system, ASP, C# as the development language, Dreamweaver, Visual Studio as the development platform, an online carbon emission accounting system based on B/S structure for coal mines owned by the Coal Industry Group is designed, which realizes online carbon emission accounting for coal mines owned by the Coal Industry Group. Finally, the application analysis results show that the method proposed in this paper can not only significantly improve the efficiency and accuracy of carbon emission accounting for coal mines owned by the Coal Industry Group, but also realize online sharing and comparison of accounting results, which is conducive for the Coal Industry Group to implement targeted monitoring and improvement of carbon emissions for coal mines owned by the Coal Industry Group.