Frequent military interventions and regional wars in the post-Cold War years have strengthened the role and position of the military factor in the international relations. This kind international political atmosphere is a major incentive for a number of countries including China, which are not match the values or interests of those countries who often lunched the military actions, to pay higher attention to their own military condition and modernization. At the same time, Sino-US relations has gone through a process of strategic trust during the later of Cold Wars years to mutual-suspicion after the end of Cold War. This change influences the basis of China’s overall strategy including defense strategy. The missile defense plan of US has been regarded as a powerful threat to China’s minimum nuclear capability. The US returning to Asia and Pacific with high military character in recent years is making the security environment around China deteriorating. Among the diversified motivations of China’s nuclear modernization, the factor of the US should take the first place. Exploring the ways of dealing with Sino-US relations, esp. the military relations could be helpful for avoiding arms race between two big countries.