This study is to explore the Post-COVID-19 international order through caused process. The findings of this study are followed. The COVID-19 outbreak ended in a short period of time brought in the protectionism due to the collapse of the GSC, low growth, and high unemployment. The rise of China may accelerate power transition between US and China, which could intensify the US-China relations from strategic rivalry to 'New Cold War'. If the COVID-19 prolongs more than 4 years, the world will suffer from the great depression. Under the great depression "economic nationalism" is likely to replace globalization, and international trade will be done on strict reciprocity. In international politics, The U.S. and China can voluntarily reduce their global roles, which transform G2 into a multipolarity. Moreover, the weakness of global governance and the absence of a world police state could lead to an rule-less anarchy. International disputes are intensified, self-reliance is strengthened, and states seeking low-cost and high efficiency security means will be tempted by WMD. The relationship between the US and China is likely to develop into uneasy, fluid coexistence.