Having used the descriptive- analyzing- deducing method, in this research, the situation of the Iranian captives and slaves of the conquests period will be studied. The findings of the research show that a great part of captives were massacred in the process of conquests. Men were the main victims. Nevertheless, some of them with women and children who included a great part of prisoners as slaves were dispatched to the Arabic lands. The slaves enjoyed with little rights and did low jobs. But, some of male slaves succeeded in acquiring a better situation by learning religious and literary sciences and in some cases were freed from slavery. The female slaves have no share from the promotion. Most of them were bought and sold as bond-maid and slave, or married the Arabs, slaves and mawali. Having studied the lineage of transmitters of hadith whom recorded in the Tabaqat al-kubra of Ibn Sa'd it will be proved that slaves had a considerable share in the population component of Hijaz.