In this paper by considering the importance of the independence of South Sudan in 2011 and the breakup of one of the largest African countries, and considering the influence of two main factors including internal and foreigner factors in the process of South Sudan independence, is seeking to understand the influence of these factors on the independence of South Sudan. Present paper attempts to describe several issues related to Sudan including the conflict in southern Sudan and northern Sudan since independence until the beginning of the new century, Bashir's government policy towards regional issues, and the motives and interests of America's foreign policy toward Sudan and the entire region. Findings of this study showed that since Sudan's independence in the 1950s, except for a brief period of peace during presidency of J. Alnmyry, was involved in the crisis of civil war between southern rebels and the central government. However several factors such as the pressure of America on the Sudanese government at the beginning of the current century, support of southern rebels by various countries such as US, Uganda, Kenya, Libya and Egypt, and the motivation to control the energy resources of Sudan, the financial and informational supports of southern rebels by the Zionistic regime, and lack of association between Sudan's Islamist government with regional policies of other countries resulted in accelerate the process of independence and separation of southern Sudan from the central government.