Central bank bills, namely, the central bank tickets, are short-term debt securities issued by the central bank to regulate the excess reserves of commercial banks. In essence, they are central bank bonds. They are called "central bank bills" in order to highlight their short-term characteristics (from the issued central bank bills, the shortest duration is 3 months and the longest is only 1 year). The purpose of issuing bills by the central bank is to withdraw funds, freezing the excessive market funds in the central bank, thereby alleviating inflation pressure on the market. This belongs to one kind of monetary policy.