Rybakina, who stunned Swiatek in the fourth round of the Australian Open before falling to Aryna Sabalenka in the final of the year's first Grand Slam, out-lasted 76th-ranked Czech Karolina Muchova 7-6 (7/4), 2-6, 6-4.
"She's playing really well and in semi-finals you always are going to play against the top players, so I'll be ready," Swiatek said. "Last time we played was in Australia. Totally different conditions. So I'll just prepare the same as before any other match and I'll do 100%."
Swiatek, in her 50th week at number one, is vying to become just the second woman after Martina Navratilova in 1990-91 to win back-to-back titles in the combined WTA and ATP Masters 1000 event in the California desert.
She hasn't dropped a set so far in a week that has seen her take down former US Open champions Bianca Andreescu and Emma Raducanu.
Romania's Cirstea, ranked 83rd in the world and coming off an impressive fourth-round victory over fifth-ranked Caroline Garcia, did all she could to stick with Swiatek early.
She recovered an early break and fended off a break point as she leveled the opening set at 2-2.
But Swiatek, adjusting to the warm daytime conditions after two straight night matches, won the next eight games to take a stranglehold on the contest.
Cirstea did save a first set point with an ace, giving herself a game point with a superb spinning drop shot before finally succumbing to Swiatek's pressure with a forehand into the net.
In a flash Swiatek was up 4-0 with two breaks in the second, Cirstea clawing one back and holding for 4-2 in a spirited display before Swiatek closed it out.
"The most important thing for me is that I came back in the second set to finish it properly," Swiatek said. "And I'm happy that I played so intense that I could start both sets well."
She'll face her biggest test of the week against Kazakhstan's Rybakina, who had all she could handle from the oft-injured Muchova.
The Czech had also reached the quarter-finals at Dubai last month but had to withdraw with an abdominal injury.
Rybakina took advantage as Muchova's serve speed dropped in the final set, but needed three match points to close it out. She wasted two with a pair of backhand errors as Muchova held serve in the penultimate game.
Rybakina then fell behind 0-30 on her serve, but polished it off after two hours and 45 minutes with her sixth ace of the day.
"Well, I didn't start the match so good," Rybakina said. "I was a bit low on energy, didn't move that well. Didn't serve (well) also.
"Also, Karolina, she played really well. She was opening the court and using these slow conditions. In the third, I just knew that I have to push more, try to focus on every point, somehow raise my energy."
Two men's quarter-finals were on the slate, with top-seeded Carlos Alcaraz taking on Canadian Felix Auger-Aliassime and defending champion Taylor Fritz facing Italy's Jannik Sinner in a battle of big-hitters.
Alcaraz, ranked second in the world, can return to number one with a third career Masters 1000 title this week, but he'll have to get past Auger-Aliassime for the first time to do so.
The 10th-ranked Canadian, who survived six match points in a fourth-round win over Tommy Paul, has won all four of their prior matches, most recently a straight-sets victory in Basel in October as a late-season surge saw Auger-Aliassime win three straight ATP titles.
The other semi-final berths were decided on Wednesday, when Daniil Medvedev -- chasing a fourth straight ATP title after victories at Rotterdam, Doha and Dubai -- beat Alejandro Davidovich Fokina of Spain 6-3, 7-5 to set a clash with American Frances Tiafoe, a 6-4, 6-4 winner over former champion Cameron Norrie of Britain.
Sabalenka also advanced, blowing past American Coco Gauff 6-4, 6-0 to book a meeting with 2022 finalist Maria Sakkari, who downed two-time Wimbledon champion Petra Kvitova 4-6, 7-5, 6-1.
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