This study was started from a hypothesis in which the geostrategy of Algeria would be a major variable on the establishment of security in Sahel-Sahara. As the most barren land in the center of the Sahara Desert in Africa, Sahel is complexly interrelated with many issues like anti-government armed group, terrorism by Islamic extremists like AQMI, illegal immigration/refugee, and human/drug trafficking through many countries. As an oil producer and military power, Algeria is facing the border(total 4,279km) with countries like Mali, Libya, Niger, Tunisia. It is also the geopolitical center that not only connects Europe and Africa across the Mediterranean, but also draws the conversion between Islamic culture of Maghreb and Christian culture of sub-Saharan region. Thus, the Sahel security policy of Algeria is closely related to the regional integration and the establishment of sustainable security of West Africa. However, Algeria’s security policy towards Sahel failed overall, which is even jeopardizing the traditional relationships with surrounding countries except for Morocco. Without any clear geostrategic vision to establish such realistic diplomatic policies, Algeria’s diplomacy towards Sahel issues was not ‘national diplomacy’, but ‘regime diplomacy’. For this reason, Algeria that is not attending the G5 Sahel which could be the core of Sahel security, is isolated by Sahel neighboring countries. Thus, the constitutional amendment and national consensus in the new government by Abdelmadjid Tebboune would become a crucial turning-point of policies towards Sahel.