The group carried out its first "smiling task" on Saturday at a local theatre, where they grinned at every visitor and asked people if they needed help.
"We smile at the mirror to determine whether our smiles are acceptable"
smile team leader
Xu said the smilers would be recruiting more members and teams would be deployed at the 2010 World Expo, which has been touted by the Shanghai government as a coming-of-age party for the East Asian boomtown.
Attempts to generate warmth among strangers in China have had mixed success.
In October, volunteers offering "free hugs" to people in a busy shopping street in Beijing were detained by police for questioning.