Diplomatic input constitutes the domestic dimension of Chinese diplomatic transformation as well as the materialistic condition of its success. Diplomatic input is not only one of the sources of diplomatic influence, but also the precondition for the operation and quality of diplomacy. It consists of both financial resources allocated to diplomacy and expenditures by diplomatic agencies. If one compares Chinese diplomatic input to Chinese defense budget and the U.S. diplomatic input, however, it becomes apparent that Chinese diplomatic input is in urgent need of increase, the adverse trend has to be reversed, and more diplomatic resources shall be devoted to those agencies in charge of diplomacy. The change of international system and the rise of China improve the cost-benefit ratio of diplomatic input as well as its marginal returns.