Down scored three second-half goals to easily overcome the Saffrons in the All-Ireland third round qualifier at Casement Park on Saturday night.
The Mourne men raced into a four-point lead but Antrim hit back and trailed 0-6 to 0-5 at the break.
Antrim moved ahead before two goals in two minutes from Conor Laverty and Martin Clarke put Down in control.
Caolan Mooney's goal sealed the win, which sets up a repeat of last year's All-Ireland final against Cork.
There was controversy in the first half when Kevin Niblock appeared to be pushed as he was about to shoot on goal, but the referee waved played on.
Mark Poland hit four frees for Down in the first half while Paddy Cunningham registered Antrim's first score after 18 minutes.
Gerard O'Boyle gave the Saffrons the lead for the first time just after the restart but that was the cue for Down to move up a gear.
The quick-fire goals from Laverty and Clarke swung the game decisively and Down were six points ahead when minor star Mooney found the roof of the net.
Antrim boss Liam Bradley, who revealed that Paddy McNeill and Niall Conway were leaving his backroom team, was proud of his side's display in defeat.
"We're really disappointed, which shows how far this team has come in the last three years," said Bradley.
"The scoreline does not reflect the effort my lads put in and there was a blatant penalty when Kevin Niblock was pushed.
"After half-time we played all the football but didn't take our chances - Down are capable of scoring goals, they did and it was curtains for us.
"I will sit down and talk to the Antrim board about my future but I've enjoyed my three years here.
"I've enjoyed Antrim football and it is on nights like tonight that I like being a county boss."