The "subprime crisis" refers to a situation that occurred in the United States in which investment funds were compelled to close due to the bankruptcy of subprime mortgage institutions, causing stock market volatility brought on by the financial storm. This situation occurred between 2006 and 2009 and is referred to as the bubble economic crisis. It caused a liquidity crisis in the major financial markets around the world. In the spring of 2006, the "subprime mortgage crisis" in the US started to manifest. The Taylor rule argues that expansionary monetary policy is the cause. The housing bubble in the United States and expansionary monetary policy are the subjects of this essay. As a result of the analysis of related phenomena, this paper concludes that the subprime crisis is caused by expansionary monetary policy.