Mao Yin was just two years old when he was snatched outside a hotel in the Chinese city of Xi’an in 1988.
He was sold to a childless couple in the neighbouring Sichuan province, according to Chinese state broadcaster CCTV.
Authorities said they were still investigating the initial abduction and further information about Mao’s adoptive parents was not released.
He was raised by them as Gu Ningning, without knowing his biological parents had been searching for him for more than three decades, police said.
In late April, police in Xi’an received a tip-off that a man in Sichuan province had bought a child from Shaanxi in the late 1980s, according to state media.
The police used facial recognition technology to analyse an old photo of Mao as a boy and came up with a simulated image of him as an adult, which was then compared with photos in the national database, according to CCTV.
After a series of investigations and comparisons, the police tracked down a man in the city of Mianyang who resembled the image of Mao. He was later confirmed to be the missing son using a DNA test, Xinhua reported.
Mao, now 34, was then reunited with his biological parents at a news conference held by the Xi’an police.
“I don’t want him to leave me anymore. I won’t let him leave me anymore,” his mother, Li Jingzhi, said as she tightly held her son’s hand.
Mao, who now runs a home decoration business in Sichuan, said he would move to Xi’an to live with his biological parents, according to CCTV.
Following Mao’s disappearance, his mother quit her job and devoted herself solely to the search for her son.
She sent out more than 100,000 flyers and went on numerous national television programmes.
She also became a volunteer, collecting information about other missing children and helping 29 of them reunite with their families.
Authorities in China say they have helped reunite more than 6,300 children with their families since the Ministry of Public Security set up a nationwide DNA database in 2009 to match parents with missing children.
According to CCTV, Mao had seen Li talking about her missing son on television before and was moved by her persistence, but did not realise he was the boy she had spent decades looking for.
This report was produced by Al Jazeera NewsFeed’s Hassan Ghani.
For more news your way, download The Citizen’s app for iOS and Android.
Download our app and read this and other great stories on the move. Available for Android and iOS.