1. investment method: national debt: national debt is issued by the national government. Investors' purchase of treasury bonds is equivalent to lending money to the government, and the government pays interest to investors and repays the principal at maturity. Treasury etf: Treasury etf is an exchange-traded fund, similar to stocks, and its portfolio mainly includes treasury bonds. Investors can buy and sell etf shares of government bonds through the stock exchange instead of buying government bonds directly.

2. Risk and reward: national debt: the investment risk of national debt is low, the national government's credit quality is high, and the default risk is small. National debt has low risk and low return. Treasury etf: Due to its structural reasons, the price of treasury etf will be affected by market supply and demand and trading behavior, which is highly volatile.

3. Investment threshold: national debt: buying national debt requires a large investment threshold, and the minimum face value of national debt is high. Treasury etf: The purchase threshold of Treasury eft is low, and investors can buy the share of ETF.