She beat fellow American Jennifer Capriati in a close three-set battle on Centre Court.
Capriati took the first set quite easily 2-6.
Grand Slams
But defending champion Serena fought back to take the last two sets 6-2 6-3.
Serena is on a roll of winning tournaments. She has won four of the past five Grand Slam titles.
The 21-year-old now faces either Belgian third seed Justine Henin-Hardenne or Svetlana Kuznetsova of Russia.