Bilad al-Sudan, which includes southern parts of Sahara Desert, has remained a mysterious and undiscovered land for centuries due to unfavorable climatic and biological conditions, water scarcity, and restrictions on the movement of people from other lands. Even the Islamic rulers did not pay attention to these areas during the conquests of North Africa and did not try to conquer these areas except for some limited campaigns, due to this fact, Islam did not enter these areas and the natives under the desert became acquainted with Islam over time and gradually due to the movement of Muslim businessmen or the migration and residence of some opponents of the government or religious scholars in this area. lack of knowledge about this land is obvious in the works of Muslim geographers-who from the third century have written valuable works in identifying different lands from far or near; For example, the exact area under the desert is not very clear in their works, and they often suffice with vague references to this area and mentioning parts or cities of it. This research, by examining the geographical works of painters until the end of the eighth century, has tried to answer this question that to what extent has the knowledge of geographers been from the sub-desert land? Or that To what extent have their works influenced the portrayal and enlightenment of Muslims in the unknown sub-Saharan region, and what sources did they use in compiling their material, and to what extent is this material true or contradictory based on current information? This research has been done with descriptive analytical approach. The results of assay have proposed that this land due to its weather situation, unrecognized paths and its natives had been less known in compare with north, east and west lands of Africa continent. However, with the expansion of trade, travel, and even the migration of a number of Muslims to these areas, geographic information from the sub-Saharan region also increased.