Both won in straight sets on Friday, with Radwanska seeing off Angelique Kerber for the loss of only two games and Petrova producing an upset in knocking out Samantha Stosur.
Russian Petrova, who was named as a 17th seed when her 13th-seeded compatriot Maria Kirilenko withdrew before the tournament with an injury, was an impressive 6-4 6-2 winner over former US Open champion Stosur.
She had a low first-serve percentage but still managed to fire nine aces and did not allow her Australian opponent to make any inroads, defying the eighth seed on the three break points that Stosur had.
Polish third seed Radwanska has earned titles this year in Dubai, Miami and Brussels, and on the basis of her form against Kerber will take some stopping in the final.
Radwanska posted a crushing 6-1 6-1 win over the German fifth seed, a player she also knocked out in the Wimbledon semi-finals in July.
The 23-year-old will not be taking Petrova lightly in the final, which will be the 23rd of the 30-year-old Russian's career and Radwanska's 14th.
Radwanska said on wtatennis.com: "Nadia has been playing great tennis the whole week. First of all I'm very, very happy I could reach the final and fight for the title again. I'll try my best - it's the final, the most important match of the week."