Total managing director Patrick Pouyanné is to attend the ceremony in person, the Iranian oil ministry said on Sunday.
The French company will take a 50.1 percent stake in the project, with CNPC taking 30 percent and Iran's Petropars 19.9 percent.
Total will invest an initial one billion dollars for the first stage of the 20-year project.
The gas produced at phase 11 of the South Pars field will "feed into the domestic Iranian market starting from 2021", a Total spokesman told the AFP news agency in Paris.
The company will "implement the project with the strictest respect for national and international law", he said.
Signing postponed because of Trump
A preliminary deal was signed in November last year and it should have been finalised at the beginning if this year.
But Pouyanné said in February that the group was holding off from signing until President Donald Trump's policy on Iran had become clear.
Trump's administration has taken a tough line on Iran and imposed fresh sanctions related to its ballistic missile programme and military activities in the region.
But the White House has not sunk the nuclear deal that led to the partial lifting of sanctions, continuing to waive the relevant sanctions every few months as required under the agreement.
US hostility has discouraged some companies, notably banks, from working in Iran.
World's econd-largest gas reserves
French companies were keen to do business when the sanctions were lifted, however, and carmakers PSA and Renault have already reached agreements to invest in the country.
Total hopes that the gasfield project will lead to others in Iran, which has the world's second-largest gas reserves, after Russia, and the fourth largest oil reserves.
The French firm led development of phases two and three of South Pars in the 1990s and had signed up to develop phase 11 in 2009.
But it was forced to abandon its projects in Iran in 2012 when France joined European Union partners in imposing sanctions because of Iran's nuclear programme.