The earning rate curve of national debt shows the relationship between the earning rate of a group of listed national debt at a certain point and left time. China's earning rate curve of national debt basically belongs to smooth kind. The change between national debt earning rate and national debt allotted time shows smooth condition, which indicates that there are problems in the issue of national debt of China. The author suggests that reasonable strucfure of interest rates of nationae debt should be established and the phenomenon of the upside-down relationship between national debt allotted time structure and interest rate structure should be eradicated.