Southern said engineering work is taking place between Ore and Rye, closing all lines between Ore and Ashford International today and tomroow (Sunday, April 22).
Trains will only run between Brighton and Eastbourne and Hastings and Ore.
Rail replacement buses will operate between Ashford International and Hastings.
Elsewhere in the county engineering work is taking place between Woldingham and East Grinstead and Uckfield, closing all lines today and tomorrow.
The M23 is also closed to motorists due to resurfacing work northbound between J10 A264 and J9. A detour is in operation.
Traffic for Gatwick will exit at J10 and divert through Crawley using the A2011 Crawley Avenue and A23.
Traffic for the M25 will exit at J10 and divert via A264 and A22 to M25 J6.
The section of road is closed until Monday morning (April 23).