In this article, we try to study deserts of Iran on the basis of geological specifications with the help of 1:100000, 1:250000 scaled maps of G.S.I and N.I.O.C using Geographical Information System (GIS) methodology. Then quaternary and evaporate formations in every study province were recognized. Saline and evaporatic formations were determined as “primary deserts”. With overlaying drainage network on the basic map of Quaternary formations, the secondary deserts were recognized. Both of these processes (The primary and secondary deserts) have formed provincial deserts. After recognition of the provincial deserts in the country map by utilization of the coordinate system of Iran's map georeferences and control check point all desert units were set up on the whole country map. Results showed that 12.6% (208041 km2) of Iran is known as deserts formed by evaporate formations.