The essence of international security is common security，which relies heavily on basic consensus on security concepts and strategies among nations. However，since the beginning of the 20^th century，such a consensus or value basis has become very “thin” as a result of the following four factors：the inception of the global international system along with its cultural diversity；the great changes in political，economic and military arenas；the rise of nationalism and popular politics；and the emergence of superpowers and their antagonistic ideologies. Within strategic culture，there is juxtaposition between confrontational culture and cooperative culture. In security concepts，people have different preferences for national，international or global security. In terms of security strategies，there exist several competing models such as hegemonic stability，balance of power and institutional cooperation. The primary aims of international security remain：avoiding major wars，maintaining the stability of the international system and safeguarding the integrity of the nations. There are two new challenges：promoting global economic justice to avoid any domestic or international conflicts caused by an imbalanced international economic order；and meeting the challenges of various non-conventional security issues affecting human life on a global scale. In an era of security interdependence，the international community must make joint efforts to rebuild the consensus on security in light of the fundamental values of common security and cooperative security，and to practice a truly “international” security strategy so as to break away from the security dilemmas inflicted by each nation’s reliance on its own self-help and competing “national” security strategy.