The main reason is that the cash flow of bonds is predictable under the condition that they are not expected to default (the coupon rate of bonds is generally fixed, and the principal of the due repayment amount or the agreed resale price is also fixed).

On the premise of predictable cash flow, the increase of interest rate will lead to a decrease in the amount of cash flow converted into present value, which will lead to a decline in bond prices. This will lead to an increase in bond yield to maturity, but a decrease in bond investment yield. The main reason is that the profit of bond investment has two aspects.

Bond investment can earn a fixed interest income, but also can earn the difference between market transactions. With the rise and fall of interest rates, if investors can buy and sell in time, they can get more benefits.

Since it is agreed that the principal and interest can be paid after maturity when the bond is issued, its income is stable and safe. Especially the national debt, the payment of principal and interest is guaranteed by the government, and there is almost no risk, so it is a safe investment method.

Listed bonds have good liquidity. When bondholders are in urgent need of funds, they can sell them in the trading market at any time. With the further opening of the financial market, the liquidity of bonds will continue to strengthen. Therefore, as an investment tool, bonds are most suitable for investors who want to get fixed income and investors who have long-term investment goals.

In China, the interest rate of bonds is higher than that of bank deposits. By investing in bonds, on the one hand, investors can get a stable interest income higher than that of bank deposits, on the other hand, they can use the changes in bond prices to buy and sell bonds and earn spreads.