Bristol City have three players on International duty over the Easter weekend, so the game has had to be called off.
It was expected to be moved anyway on Police advice to a mid week game, so this will now happen, but no new date has yet been set.
Swindon have already beaten Bristol City twice this season 2-1 in the league at Ashton Gate in August, then 1-0 at the County Ground in November in the LDV Vans Trophy.
Tickets already bought will be valid for the re-arranged date when it is set.