An icy Halep served out the match at the end of a solid game on her own terms, converting the first match point she had.
Second-seed Halep, 26, won her first match against the Russian after seven consecutive losses, most recently about one month ago at the US Open first round.
Asked by AFP what those were, she smiled: "I tell you one, only one: to win a Grand Slam, which you know".
Romanian Halep won 6-2 6-4 in Beijing and will replace Spain's Garbine Muguruza at the top of the rankings.
Halep knew that a march to the final would see her top the world rankings when the new list is published on Monday, and she duly took care of Latvia's Ostapenko 6-2 6-4 in Saturday's semi-final.
Halep booked her place in the finals of the China Open after registering a comfortable 6-2, 6-4 win over Ostapenko in a one-sided last-four contest that lasted one hour and 15 minutes.
The former world No. 1 was forced to retire during her Beijing opener due to illness.
In the men's draw, world number one Rafael Nadal beat Grigor Dimitrov to set up a tasty final showdown with temperamental Australian Nick Kyrgios, who pulled off a stunning 6-3, 7-5 win over starlet Alexander Zverev. "It's my first victory against her and I just want to enjoy the moment".
Halep's all-round game was simply far too good for Sharapova, who made 20 unforced errors in the opening set alone. She defeats the French Open champion to advance in Beijing, winning in straight sets. At Roland Garros, she lost to Ostapenko in the final to be denied the opportunity to climb atop.
Simona will play against Petra Kvitova or Caroline Garcia in the title match tomorrow, mighty releaved she finally managed to conquer the WTA list after playing consistent tennis this season (not in the last 2 events, though, but that couldn't make the difference).