Halep, who lost to Kasatkina in the second round of last month's Wuhan Open, was never at risk of suffering a second consecutive defeat by the 20-year-old, sending down 19 winners to wrap up the win in just over an hour.
"I think I played much better than Wuhan," the Romanian said after the match. "I changed tactics and worked pretty well. I just played my game and my style, and I was very consistent and solid as well."
The tournament in Beijing has already seen Halep register a first career victory over Russian Maria Sharapova, and the second seed now has an opportunity to level her head-to-head with Jelena Ostapenko, who beat her in this year's French Open final.
Simona Halep of Romania returns a shot during the Women's singles Quarterfinals match against Daria Kasatkina of Russia on day seven of 2017 China Open at the China National Tennis Centre on October 6, 2017 in Beijing, China.
Image credit: Getty Images
The mercurial Latvian bested Sorana Cirstea 6-4 6-4 in an error-strewn quarter-final that saw both players struggling to hold serve.
Ostapenko made a typically high 33 unforced errors, but her powerful forehand kept her out of trouble against Romanian Cirstea, who is also her doubles partner.
Twice-Wimbledon champion Petra Kvitova fought off fatigue to dominate Czech compatriot Barbora Strycova 6-3 6-4 and reach her third Beijing semi-final.
Kvitova, who produced 33 winners offset by 43 unforced errors, said she was tired but very happy with the victory, and will meet Caroline Garcia in the last four.
"I couldn't just imagine this coming to Asia," Kvitova said. "I'm already happy. I love these big matches anyway, so I will do my best tomorrow.
"I felt a little bit tired today maybe. On the court I felt pretty slow. Maybe I wasn't, but that was my feeling. Sometimes it's pretty confusing."
Garcia came through a gruelling contest that stretched for three hours and 21 minutes against world number three Elina Svitolina of Ukraine in the day's final match.
Playing with her right thigh heavily strapped, the Frenchwoman lost the first set, but clung on as the clock at the National Tennis Stadium ticked past midnight to prevail 6-7(5) 7-5 7-6(6).