Sussex won by 251 runs at New Road to ensure their Division One safety.
But Worcestershire were kept sweating until the final week of the season thanks to this defeat and Yorkshire's victory over Somerset at Headingley.
James Anyon (4-55) and Amjad Khan (3-43) spearheaded Sussex's efforts to complete victory not long before tea.
Home skipper Daryl Mitchell offered resistance with 61 as Worcestershire, bowled out for 169, were left still needing eight points to be safe.
Going into their last match against title hopefuls Durham at Chester-le-Street on Monday, Steve Rhodes' men will have to be ready to cover any late move by Hampshire in their closing fixture against title-chasing Warwickshire at The Rose Bowl.
Defeat by Sussex represented a complete turnaround since last September when the two teams were promoted together and Worcestershire snatched second place by chasing 301 on the last day.
This time there was never any danger they would be let into a contest that Sussex dominated from start to finish.
Michael Yardy made sure that the home side were batted out of contention before his overnight declaration at 267-4 - leaving Joe Gatting unbeaten on 116.
That set a mountainous target of 421 in the day and Worcestershire, not surprisingly, were unable to launch any kind of challenge.
Anyon was again their quick bowling spearhead, reaching 50 wickets in a season for the first time.
And, although Monty Panesar was not as effective as in the first innings, managing a solitary success, he is still in contention to be the top bowler in Division One on 64 dismissals, now three behind the leader, Worcestershire seamer Alan Richardson.
Worcestershire director of cricket Steve Rhodes told BBC Hereford and Worcester:
"If you look at the way the first three days went and then again today, you would definitely say Sussex deserved their win.
"We wanted our 'A game' in a crucial match and we didn't get it - we got something like our 'C game'.
"That wasn't good enough and we are big enough to take it on the chin.
"I have said to the boys just now that next week now (at Durham) we have got to turn up."
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