After Donald Trump took office，the U.S. strategy toward China has undergone big adjustments. The strategy of engagement with China has been criticized and abandoned. In fact，the U.S. strategy toward China has gradually turned to contain China. In this context，the importance of the South China Sea issue in the U.S. strategy towards China has been enhanced，and the U.S. policy and action on the South China Sea issue has also been upgraded. In 2020，the United States formally abandoned its long-standing neutral position on the territorial disputes in the South China Sea and began to publicly deny China’s claims on the South China Sea. This was a big adjustment of the U.S. policy on South China Sea. In addition，the Trump administration also intervened in the South China Sea issue through diplomatic，military and economic channels. At present，the United States is stepping up its intervention in the South China Sea issue，promoting the further internationalization of the South China Sea issue，trying to use the South China Sea issue to form an anti-China alliance or united front，and is preparing for possible armed conflicts in the South China Sea region. China needs to be well prepared to meet the US challenge on the South China Sea issue.