Ricky Ponting, Australian captain, top-scored in his side's chase with 66 not-out, while Andrew Symonds (63 not out), Matthew Hayden (41), Adam Gilchrist (30), and Michael Clarke (23), all chimed in with runs to seal victory in the 43rd over.
The Sri Lankans chose to rest Vaas and Muralitharan, while Malinga continues to recover from injury, with Australia pressing ahead with their strongest line-up, although all-rounder Shane Watson was still out through injury, replaced by batsman Brad Hodge.
"It's not the way we would have done it but they're a different team," said Symonds on Sri Lanka's decision to rest Vaas and Muralitharan.
"They are key players. It can affect confidence when you do that."
The decision was defended by Sri Lankan captain Mahela Jayawardene, and may have been tactical ahead of a possible meeting with Australia in the final.
"We have to do what's best for the team and that's why we took the decision," said Jayawardene.
"We use our personnel on and off and we have to make sure we have the guys ready for the semi-finals."
Sri Lanka won the toss and elected to bat on a good wicket, but apart from Chamara Silva and the captain himself, their batting line up didn't offer much resistance as they were dismissed for 226 in their 50th over.
After Sri Lanka's top three batsmen went for a total of 18 runs, Jayawardene (72) and Silva (64) put on a 140-run stand for the fourth wicket and had their side on top at 167 for 3, before spinner Brad Hogg dismissed both established batsmen in two overs.
Earlier, Australian left-arm seamer Nathan Bracken had removed openers Sanath Jayasuriya LBW for 12, and Upul Tharanga caught by Hayden for six, while Glenn McGrath trapped the dangerous Kumar Sanggakara leg-before for a duck.
However Jayawardene and Silva steadied the ship and managed to score at around four runs per over in the middle stages, with paceman Shaun Tait going for plenty of runs and finishing with 2 for 68 from his ten overs.
Sri Lanka lost their final six wickets for just 59 runs with some late resistance from bowlers Farveez Maharoof (25 off 22 balls), and Malinga Bandara (17) getting the total past the two hundred mark.
Bracken turned in a player of the match performance when taking 4 for 19 off 9.4 overs, while Hogg and McGrath took two wickets apiece.
The chase was all too easy for Australia against a depleted bowling attack, with Hayden and Gilchrist putting on 76 for the first wicket to lay a good foundation for the low run chase.
|That's out: Umpire Aleem Dar, top, gives Sri Lankan batsman Kumar Sangakkara |
out for zero, leg before wicket to Glenn McGrath, centre, [AFP]
"Right at this moment it's all about momentum," said Ponting.
"We've played some good cricket and we're looking to carry that momentum into the semi-finals.
"Our batting was again very good and another good start gave a platform for the rest of the guys to chip away."
Australia remain undefeated in the tournament and play second placed New Zealand in their final Super Eight match on Friday, which could decide which team finishes on top of the table going into the semi-finals.
Sri Lanka are in no danger of missing out on the semis and will finish in either second or third place regardless of the result in their final Super Eight match against Ireland in Grenada on Wednesday.