The empirical analysis in this paper indicates that the effect of Chinas national debt on monetary supply is huge. At the same time, this paper puts forward the theoretical condition of optimal issuance scale of national debt, analyses the effects on all levels of monetary supply when the new issued national bonds were purchased, analyses the effects of the time of the issuance of ithe national debt on time structure of monetary supply, and presents that the coordination countermeasures between financial policy and monetary policy to better realize macro--adjustment of the government.