It was all over in 38 minutes, with Ioannis Amanatidis and a brace from Martin Fenin putting Frankfurt three goals ahead. Marcel Heller added a fourth late in the second half, either side of Claudia Niculescu and Markus Daun consolations for Duisburg.
Duisburg looked to have avoided bottom spot even in defeat, but Hansa Rostock's late winner against Bochum saw them finish 17th instead. Eintracht finish ninth - a marked improvement on 14th place in 2006/07.
Frankfurt were in buoyant form as soon as the game kicked off and by the 13th minute they were ahead. The ball fell to Amanatidis in the middle of the penalty box and he got power behind his shot, giving goalkeeper Tom Starke no chance.
Two minutes later, it was 2-0. More slack defending allowed Fenin to get under the ball as it dropped and he caught it sweetly on the volley before Starke could get there.
Niculescu then hit the post for Duisburg, before Fenin put Frankfurt into an even more commanding position in the 38th minute. A corner from the right came through a maze of bodies to the Czech Republic striker, who prodded the ball home.
Come the second half, it was the visitors who came back into it. Niculescu could not really miss from close range and he gave goalkeeper Markus Proll no chance.
Even at 3-1, Eintracht never looked like being caught and they made sure of the points in the 78th minute. Michael Finx's through-ball played in Heller, who shot to the right of Starke and into the net.
There was still time for Duisburg to use their last few minutes of life in the Bundesliga to grab an 86th-minute consolation. The Eintracht defence were sound asleep when an unmarked Daun tried his luck on the left of the penalty area and he made no mistake.