Midfielder Huang Zhengyu’s shot from the right wing in the 20th minute was the difference in the tightly-contested affair at the EAFF E-1 Championship.
China, ranked 94th in the world, came close to extending the lead later.
A shot by striker Zhang Yuning hit the bar.
Minutes later, winger Wang Yudong’s effort from close range needed a finger-tip save by Hong Kong, China captain and goalkeeper Edmond Yapp, which then came off the post.
The national team also had two goals disallowed.
China’s caretaker head coach, Dejan Djurdjevic, who only took over less than three weeks ago, said he’s happy with the result.
“We deserved to win… we scored one goal and after that, we had many, many good opportunities to finish [off] the game, we were unlucky,” he said after the match.
“The approach of the players was very good.”
Hong Kong, China’s head coach Ashley Westwood said the tournament in South Korea was an eye-opening experience for his squad.
“We’re satisfied with the desire and commitment the players showed – obviously we’re not satisfied with losing, we never are,” he said.
“We have to take lessons. We’ve improved throughout the tournament, we only conceded one goal [this time].”
The SAR finished the tournament with three straight defeats, after losses of 1-6 to Japan and 0-2 to South Korea.