Up to 7,000 fans and hundreds of reporters, including some from South Korea and the United States are part of the event.
During the past 10 years, the previous four Transformers movies totally earned nearly 3.8 billion yuan ($560 million) in China, making it one of the most commercially successful Hollywood franchises in the world's second-largest movie market.
The most stunning performance was by the fourth movie, Transformers: Age of Extinction, which topped world box-office charts in 2014.
The movie raked 1.97 billion yuan in China, around 35 percent more than the $2.33 million from North America.
To celebrate the 10th anniversary of the Transformers franchise, Paramount chose Guangzhou for the promotional event from 20 Chinese cities in an online campaign that received 6 million votes earlier this year.
In the movie, Mark Wahlberg reprises his role as the Texan inventor Cade Yeager, while Duhamel returns as Lieutenant Colonel Lennox.
Duhamel, who appeared in the first three films but did not perform the fourth, says it was a big surprise for him when he was invited again.
He says the movie has changed his life, making him feel a part of the franchise.
In the film, Yeager faces the biggest challenge of his life-being chosen to save the world, through an unlikely teaming up with a streetwise tomboy, a sagacious English aristocrat and a beautiful Oxford scholar.