The three-time Grand Slam champion is homing in on her first title of the year and has now reached the semi-finals in her last four grass court events.
The German broke twice early in both sets to take a commanding lead in the battle between two former world number ones.
Halep got one of the breaks back on both occasions, but Kerber held on to seal victory in just over 70 minutes.
Next up she will face the unseeded Ons Jabeur for a spot in the final after the Tunisian edged out Alize Cornet 1-6, 7-5, 6-3.
The two top seeds on the other side of the draw will clash for a place in Saturday's final as world number three Karolina Pliskova and fourth-ranked Kiki Bertens claimed a place in the last four.
Pliskova, who won in Eastbourne two years ago, dropped just two games outclassing Russia's Ekaterina Alexandrova 6-2, 6-0.
Bertens had a tougher afternoon, but eventually saw off last year's finalist Aryna Sabalenka 6-4, 3-6, 6-4.
Eastbourne ATP/WTA results on Thursday (x denotes seeding):
Taylor Fritz (USA) bt Hubert Hurkacz (POL) 6-4, 7-6 (7/5)
Kyle Edmund (GBR x3) bt Daniel Evans (GBR) 1-6, 6-3, 6-4
Sam Querrey (USA) bt Fernando Verdasco (ESP x5) 7-6 (7/4), 6-2
Thomas Fabbiano (ITA) bt Gilles Simon (FRA x6) 6-4, 6-3
Ons Jabeur (TUN) bt Alize Cornet (FRA) 1-6, 7-5, 6-3
Angelique Kerber (GER x4) bt Simona Halep (ROU x6) 6-4, 6-3
Kiki Bertens (NED x3) bt Aryna Sabalenka (BLR x8) 6-4, 3-6, 6-4
Karolína Plíšková (CZE x2) bt Ekaterina Alexandrova (RUS) 6-2, 6-0