The military conflict，erupted on December 15，2013 in the South Sudan capital Juba，has not only direct reasons but also deep social roots. The challenges for South Sudan and the controversial issues between the two Sudans indicate that this civil war had been hard to avoid. After the fighting broke out，the international community had tried hard to take necessary measures to stop it. For the domestic principal contradictions remain in South Sudan，this civil war will not end in a very short time.