Fu - from Happy Valley in Hong Kong - was far from happy with the condition of his game despite overcoming Shaun Murphy 4-1 earlier in the day, and it became evident that he was not going to be able to live with the defending champion as O'Sullivan coasted 3-0 clear courtesy of a 75, 71 and 62.
A 61 and 60 carried him to the cusp of victory at 5-0 up before he collected a scrappy sixth frame to secure his progress in only one hour and 23 minutes.
“Marco had a good win today against Shaun, so it was a tough match for me. I never expect an easy match against him because when I play him he seems to play well against me," said O'Sullivan.
“I was expecting a tough match, but I watched a bit of Marco’s game and you could see he was struggling a little bit and tonight he struggled with his game. You have to go out there and do a job and try and get the win.
“I am pleased to still be in the tournament, this is one of the better tournaments we play in. To still be in it and have the weekend to look forward to is great.
“Ding is the winner of five major ranking events last season and only Stephen Hendry has been able to do that in the past so that is a measure of the quality player Ding is. We have good games when we play each other, and I like playing Ding because he plays the right shots. I will look forward to it.”
O'Sullivan had opened his bid for back-to-back Champion of Champions trophies with a 4-2 win over Stuart Bingham.
In a repeat of last year's final that O'Sullivan won 10-8, the five-times world champion trailed Bingham 2-1 before producing some of his very best snooker to book his place in the Group One final against Fu.
O'Sullivan suffered a 6-4 defeat to Bingham in the last eight of last season's UK Championship, and was left pumping his fist in relief after edging pass the Basildon potter in another high-quality meeting this time.
Watched by a packed crowd at the Ricoh Arena, O'Sullivan pocketed the opening frame with a knock of 60 only to watch Bingham restore parity with 107 before 62 saw 'Ballrun' move 2-1 to the good after O'Sullivan had led 47-0.
Top seed O'Sullivan seemed to sense the warning signs over such a short format and put his foot on the gas with 83, 115 and 103 leaving Bingham down and out having hardly made an error from leading 2-1 with his opponent producing an immaculate plant on red to a centre pocket to provide the scope for moving 3-2 clear.
O'Sullivan continues to move closer to Stephen Hendry on the all-time list of the game's century makers. He moves onto 758 with the retired Hendry's target of 775 likely to be overtaken before the season is out.
2005 world champion Murphy suffered a disappointing exit. He picked up the first frame against Fu with a 50, but his performance was littered with mistakes as Fu - the highest ranked qualifier in the event without a title to his name over the past year - ran in 46, 56 and 80 to progress.
O'Sullivan faces Ding in Saturday afternoon's first semi-final while Judd Trump will contest the second semi-final on Saturday evening against the winner of Group 3 after he enjoyed a 6-1 success against world champion Mark Selby on Tuesday evening. The winner of the tournament collects a £100,000 cheque.
Champion of Champions draw and results
Monday 3rd, Group 4 (first match at 1.00pm)
Ding Junhui (1) 4-2 Dominic Dale
Barry Hawkins (2) 4-1 John Higgins
Group 4 final (7pm)
Ding Junhui (1) 6-5 Barry Hawkins
Tuesday 4th, Group 2 (first match at 1.00pm)
Mark Selby (1) 4-1 Steve Davis
Judd Trump (2) 4-1 Stephen Maguire
Group 2 final (7pm)
Judd Trump 6-1 Mark Selby
Wednesday 5th, Group 1 (first match at 1pm)
Ronnie O'Sullivan (1) 4-2 Stuart Bingham
Shaun Murphy (2) 1-4 Marco Fu
Group 1 final (7pm)
Ronnie O'Sullivan 6-0 Marco Fu
Friday 7th, Group 3 (first match at 1.00pm)
Neil Robertson (1) 4-0 Ali Carter
Ricky Walden (2) 4-0 Mark Allen
Group 3 final
Neil Robertson v Ricky Walden
Saturday 8th, semi-finals (best of 11 frames)
Ding Junhui v Ronnie O'Sullivan (1pm)
Judd Trump v winner of Group 3 (7pm)
Sunday 9th, final (best of 19 frames)
Ding/O'Sullivan v Trump/winner of Group 3