Abstract: According to Marx's credit theory, market economy is a kind of credit economy. In the credit economy, most transactions are credit transactions, thus forming a huge chain of creditor's rights and debts. In the boom period, commercial credit and bank credit are the key factors in maintaining the credit and debt chain. In the crisis period, the national credit plays a certain buffer role, but a large number of overdue debts can only enter the next economic cycle after the market is cleared. The huge amount of overdue debts formed in the great recession of the United States in 2007-2009 was cleared not by the market but by the zero-benchmark interest rate and the purchase of treasury bonds and mortgage bonds, which injected huge amounts of national credit to support commercial credit and bank credit. As a result, though the economic growth was maintained for 128 months, it was difficult to raise the Fed's benchmark interest rate to a normal level, leading to another crisis in the stock market bubble. The COVID-19 pierced the stock market bubble and led to the "Great Depression". The US government adopted the zero-benchmark interest rate and unlimited purchase of bonds to inject liquidity, and the Treasury launched a trillion economic stimulus plan. Under the negative economic growth, the stock market bubble was repaired and inflated to an unprecedented level. Obviously, even if the vaccine can end the COVID-19 pandemic, the root cause of the "Great Depression" still exists. Therefore, the "COVID-19 Depression" in the United States is a continuation of the Great Recession of 2007-2009.