Abstract:Since Joe Biden began his presidency，the US has pursued his foreign policy based on the concept of “alliance first”. In Northeast Asia，the US has comprehensively promoted its alliance with ROK，promoting ROK’s international status，strengthening up the trilateral relations between the United States，Japan and ROK，and trying to bring the Alliance with ROK into the Indo-Pacific strategy. Its aim is to take Northeast Asia as the frontline for US against China. In terms of US policy on DPRK，the Biden administration has insisted on “principled diplomacy” while downplaying the nuclear issue in his foreign affairs，aiming to strengthen coordination with the allies in East Asia. In the context of the competitive relationship between China and US，uncertainties in Northeast Asia will increase，and opportunities and challenges will coexist.