Militants publicly beheaded Khaled al-Asaad, 82, after he refused to disclose the location of valuable artefacts.
State media reported that his body was thought to be among three discovered in Kahloul, east of Palmyra.
DNA tests will be carried out to confirm their identities.
The brutal murder was one of a series of atrocities committed by IS militants during the two periods they were in control of the Unesco World Heritage site.
