Like other periods in the history of Iran، Azarbaijan has had a significant role in the historical developments of Iran، especially in the history of the Seljuk. By studying and analyzing the main sources on the history of the Seljuk، it becomes clear that from the first half of the 5th A. H. large groups of Turkmen (variedly termed as Ghoz or Oghooz) immigrated to Azarbaijan near the borders of Byzantium. From this very period، Azarbaijan has significantly functioned as the main base of the Turkmen and the Seljuqids. This study aims to answer the question that what role Azarbaijan played in the conquer of Anatolia، which was a part of the Byzantium Empire then? This study is based on a historical - analytical method. The results of the study indicated that Anatoli had a significant role both in the emigration of of the Turkmen from Azarbaijan to Anatolia and the expansion of the Seljuqs'' territories in Anatolia.