The video documented an execution that reportedly happened shortly after the group captured the city on May 21.
The 10-minute clip shows the captives being transported by a convoy of pickup trucks to the site of the Palmyra ruins, where they are made to kneel in a line in the amphitheater.
As the death sentence is read out, a crowd of a couple of hundred – including small children - can be seen on the wings of the amphitheater, Al-Arabiya reported.
The camera then zooms in on the soldiers, some of whom appear to have been beaten. They are then executed by pistol fire, and their bloodied corpses are shown lying on the ground.
The video is the latest in a series of gruesome executions released by the group.
ISIL have also begun destroying some of the ancient relics from the site, although the video released Saturday could suggest that the militants wish to keep some of the ruins intact as a convenient place to carry out executions.