Actor Ai Lun (left) stars a female journalist who exchanges soul with a boxer, played by comedian actress Ma Li (right). [Photo provided to China Daily]

When Chinese actor Ai Lun was shooting the comedy Never Say Die, he repeated his lines every morning in front of a mirror before going to the set.

Ai, who is tall at 187 centimeters and weighs 85 kilograms, repeated the line: "Remember, you are a woman."

At a recent Beijing event to promote the upcoming movie, Ai revealed his method to prepare for the role of a female journalist who exchanges soul with a masculine boxer.

Adapted from the popular stage play with the same title, Never Say Die is about the two's messy yet joyful adventures brought by the incredible exchange.

Comedian actress Ma Li, who shot to fame with the 2015 hit comedy Goodbye Mr Loser, stars as the boxer who gets into the journalist's body.

"I have closely observed the way Ai usually speaks, walks and even blinks. In the movie, I become the real-life Ai. It was such a big challenge," said the 35-year-old actress.

The film, set to open across China on Sept 30, is the third such stage play-inspired movie produced by Mahua Fun Age, one of the country's most popular comedy troupes.

The previous two are Goodbye Mr Loser and Mr Donkey (2016).