The hosts bundled out South Africa for a meagre 175 after inserting them in to bat and then comfortably overhauled the target with 12.3 overs to spare.
Such was the domination of the England bowlers that AB de Villiers and Co found it difficult to buck the trend of faltering in major ICC tournaments.
It was complete team effort by England as all the bowlers played a part in demolishing the South African top and middle batting order.
James Anderson (2/14) and Steven Finn (1/45) excelled with the two new balls and were duly complemented by Stuart Broad (3/50) and off-spinner James Tredwell, (3/19).
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England lost their openers early but Jonathan Trott (82 not out) and Joe Root (48) batted with clam and assurance to lead the hosts to the finish line. They shared a 105-run stand for the third wicket.
It is second time that England have qualified for the Champions Trophy final. The last time they featured in the final was in 2004. That time also they had hosted the event and ended runners-up to the West Indies.
England will now play the winner of tomorrow's semifinal between World Champions India and Sri Lanka in the summit clash on June 23 at Birmingham.
South African bowlers did a decent job, specially spinner Robin Peterson, but England had the luxury of wickets with a small target at hand.
Trott's knock came off 84 balls with 11 boundaries while Root helped himself with seven shots to the fence in his 71-ball knock. By the time Root JP Duminy dismissed Root, England were inches from the win.