Khomein city is located between the Iranian central plateau and central Zagros. The relative importance of Khomein in Sassanian period is evidenced by presence of distinctive monuments such as fire temple of Atashkooh and Mile Malyon in eastern part of Mahallat and inscriptions of Gharghab valley and also passing of a branch of Silk Road through it. Nevertheless there is not so much information about the Sassanians in Iranian Central plateau, specifically in Khomein. This study aimed to determine and reconstruct the patterns and distribution of Sassanid settlements bases on historical documents, environmental and archaeological data, which are gained from archaeological surveys. Hence for determining the influential factors in the formation and distribution of settlements, archaeological information of Khomein were incorporated in GIS system by providing environmental as well as historical information of the region.