Since Xi Jinping became the leader of the People’s Republic of China (PRC) at the 18th National Congress of the Chinese Communist Party (CCP) in 2012, cyber security has been the focus of U.S.-China relations. The U.S. currently holds an obvious advantage in the cyber security field, however, the PRC has been tempted to compete with the U.S. when it comes to cybercrime in the area of economic and political security, military disputes and control over domestic legislation. The PRC aims not only to realize President Xi’s pledge to become a strong cyber power, but also to challenge the leading status of the U.S.. The main purpose of this article is to assess the competitive relationship between the U.S. and the PRC under Xi’s leadership in respect to cyber security via offensive realism. The paper presents case studies on politics, economics, the military and internal control.