Hastings and Bexhill will retain their direct train links with London and Gatwick.
Rail Minister Derek Twigg made the announcement to the delight of campaigners.
The service was under threat in February after the Department for Transport published its Route Utilisation Strategy for the Brighton mainline.
It suggested London trains should stop at Eastbourne forcing passengers for Hastings and Bexhill to change.
But Mr Twigg said considerable improvements and the addition of 700 new trains on the Southern franchise meant the change was no longer necessary.
He said the introduction of new Electrostar trains had improved performance by 12 per cent and almost nine out of ten trains were running on time.
Mr Twigg said: "The Government is investing record amounts on the railway and more than 4,000 trains and carriages have been replaced, including all those on services running into London from the South Coast.
"This is paying handsome dividend and is allowing us to make even better use of the rail network."
The plan to stop London to Hastings/Bexhill services at Eastbourne was recommended as the late running of those services was having a detrimental impact on the punctuality of other mainline trains.
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