The software spent about two months sorting through nearly 100 candidates before singling out Weifeng, who is a student in the provincial capital Guangzhou.
Investigator Zheng Zhenhai said: "When he found him, he refused to believe that he was a kidnapped child, but DNA confirmed that he was a match with his biological parents.
"We opened the case the day after the incident and we never gave up.
"We checked surveillance footage, but there were simply too many people coming in and out of the area."
The emotional dad said at the reunion: "We're also very grateful to his foster parents for raising him for 18 years. From now on, his foster father will become like a brother to me; my son will have two dads."
Police said they were still investigating details of the 2001 kidnapping, with no arrests announced so far.
HOPES FOR MADELINE MCCANN
The technology used to locate Weifeng has given some hope in potentially advancing the case of finding missing girl Madeleine McCann.
Maddie vanished from the Praia da Luz resort in Portugal in 2007 aged just three at the time.
Now they're hoping the advancement in technology and face recognition could help solve the case.
The official Find Madeleine Campaign website says: "Fortunately, there are many cases of abducted children being found and returned to their families — even after long periods of time.
"The vital piece of information that leads to a happy and longed-for reunion is usually thanks to a caring and vigilant member of the general public, often recognising a face from a poster."