As the provinces successively approve the second rounds of transmission and distribution tariff (TDT), the calculation of transmission and distribution costs will continue to be refined, and the design methods for TDT will continue to be improved. Firstly, according to the load conduction relationship between transmission and distribution grid (TDG), the cost conduction model between TDG was established, and the total cost of TDG was shared fairly and reasonably among power users of different voltage levels. Secondly, according to the maximum power load of different types of users at each time point, the TDG cost of a certain voltage level was further shared among different types of users of the voltage level using the combined load method. On this basis, the TDT of general industrial and commercial users and large industrial users with different voltage levels was designed. Finally, taking province L in eastern China as the research object, an example was analyzed to verify the scientificity and practicability of the model and method proposed in this paper.