The Japanese team was a goal up early in the first half but Guangzhou turned the match with a goal in each half.
Guangzhou attacked incessantly in the second half but could not get the third goal that would have made life easier in the return in three weeks.
Gamba shook the full house at the Tianhe Sport Center in the 12th minute when it took the lead with an own goal from Feng Ziaoting.
Guangzhou reacted furiously to this setback but Gamba's defence stood firm.
The home side drew level 10 minutes from halftime with a volley from Hung Bowen.
Guangzhou continued to attack in the second half and Zheng Long was unlucky to hit the post with a free kick in the 49th minute.
Guangzhou was not to be denied because Zheng Zhi headed it into the lead eight minutes later.
In the other semi-final Saudi Arabia's Al Hilal drew 1-1 with Al Ahli of the United Arab Emirates.
