In early 2016，North Korea conducted a fourth nuclear bomb test，namely the self-claimed “Hydrogen Bomb Test”，and launched a “Bright Star No.4” Satellite，against which background the US-ROK Alliance moved into a new round of reinforcement with greater strength，depth，and width.The deployment of THAAD in South Korea received strong criticisms and oppositions from neighbouring countries，especially China，Russia，and North Korea.The US-ROK Alliance has strong military characteristics.The dramatic changes in the Korean Peninsula and Northeast Asia had led to a stronger will on the part of South Korea to strengthen its alliance with the US.This Alliance is changing towards an all-round strategic alliance that involves such areas as politics，economy，and non-traditional security.It has a clear region-specific orientation with a global vision，which may increase the risk of arm race for the whole region，rendering it increasingly vulnerable to newer and greater regional insecurity.China should formulate policy measures as an effective response to the changes in the international situation，for purpose of defending its own national core interests and promoting stability in the Korean Peninsula，as well as the peaceful development of the whole region.