As the leading power in the South Asia, India is one of the most significant influence states in contemporary international relations with a centuries-old history and brilliant cultures. Since India declared independence on 15 August 1947, driven by a variety of reasons, India has developed and applied its nuclear technology in silence, and it conducted first “peaceful nuclear explosion” in 1974. Until the openly nuclear test in 1998, India has become an actual nuclear weapons state and continually improved its nuclear process. It has taken a distinct way to develop its nuclear weapons that experienced the peaceful nuclear policy to not give up the nuclear option to openly nuclear deterrence. The thesis takes India’s nuclear strategy as research object and answered why India insist on developing nuclear weapons. With the clue of time, this article attempts to elaborate systematically the evolution of India’s nuclear policy since its independence. This part would investigate in detail that the main leader’s attitude toward developing nuclear weapons in Indian history and present the transformation process of nuclear policy. Although strategic issue research generally use the theory of realism to analyze, this thesis would consult the resource-extractive model of neoclassical realism to explore the limiting and motivating factors of developing nuclear weapons over half a century in India through two major case studies. Obviously, there are multiple motives would facilitate India to implement nuclear policy and gradually walk on the path of nuclear deterrence. Its behaviors not only out of its national security concerns but also 3 aim at challenging the global nuclear regime. With the guidance of resource-extractive model, this paper would not only analyze the level of external threat or vulnerability but also explore how the Indian state power contribute to India’s nuclear policy. Last but not the least, the relationship among these three variables is demonstrated that Indian state power influenced by the external threat and the international environment before making decision, and the formulation of nuclear policy also is determined by the external vulnerability with a certain degree of instigation from domestic power.