Eoin Morgan's side will lock horns with New Zealand at Lord's on Sunday as both teams aim to lift the trophy for the first time.
It was a massive moment for Strauss, who was drafted into the role by the ECB after England’s horrible run in the World Cup 2015.
Strauss played a huge role in the appointment of Trevor Bayliss and urged the ECB to place more emphasis on white-ball cricket which saw them rise to the top of ODI rankings.
He stepped down from the role in October last year to spend more time with his family after his wife was diagnosed with lung cancer.
"That was England's best performance of the World Cup," Strauss told broadcaster Sky Sports.
"England absolutely obliterated Australia with bat and ball. The way (Chris) Woakes and (Jofra) Archer set the tone was fantastic.
"And with the bat, I mean it was just outstanding batting from (Jason) Roy in particular. Now is not the time to talk about the Ashes but the way he lined up (Mitchell) Starc, I thought he was fantastic.
"It was the ultimate performance. England will go into that final with just incredible spirits, huge confidence and they will be confident they can put New Zealand away as well.
"I was getting quite emotional watching that today. All I ask from this England team is to play the same way on Sunday."
Meanwhile, Australia legend Shane Warne admitted England were deserved winners of the semi-final and backed them to lift the trophy on Sunday.
"Disappointing from a Australian point of view, but they were outplayed by England from the word go," Warne said.
"England showed their class, I thought Eoin Morgan was world class. He manipulated his bowlers well, he could have easily backed off but he didn't.
"He brought Archer back earlier to go for it and (Adil) Rashid was the real ace for Morgan today.
"England seem to be peaking at the right time and that's what you have to do to win World Cups."