The last-four pairs contest was very close as both the teams broke each other four times and Sania and Soares won overall 74 points, only three more than their rivals.
Sania and Soares are up against unseeded pair of Abigail Spears from the USA and Santiago Gonzalez from Mexico.
It will be Sania's fifth mixed doubles final appearance at the Grand Slam level, having won Australian Open (2009) and French Open (2012) with compatriot Mahesh Bhupathi.
The 27-year old had reached the Australian Open mixed doubles final this year also but ended runners-up with Romanian partner Horea Tecau.
Sania also has the opportunity to reach only her second women's doubles final at Majors as she prepares to take on Swiss comeback queen Martina Hingis and Italian Flavia Pennetta in the semifinals.
All other Indians have already exited from the last Grand Slam of the season as Rohan Bopanna and Leander Paes fell at different stages of their respective events.
There was no Indian playing in the men's singles as Somdev could not qualify for the main draw.