The 38-year-old broke the deadlock in the 34th minute as Theo Hernandez whipped in a cross from the left and the Swede out-jumped two defenders to steer his powering header into the net.
Guoan suffered criticism after earlier fumbling a 3-0 lead against Qingdao, suffering instead a 3-3 tie in the first leg.
"I was trying to find my rhythm and enhancing my cooperation with my teammates in today's match because I have long been out of formal games this year," said Tianjin captain Li.
The result left Boca with 10 points from four matches in Group H, three points clear of second-placed Caracas FC. Independiente Medellin remained at the foot of the group with four straight defeats.
Both sides accelerated their rhythm in the second set, but Hebei could hardly break through the tight blocks cemented by Xu Ruoya and Wang Chenyue as Jiangsu had an identical winning scoring for the second set.
Without Kun Aguero, Aymeric Laporte and Ilkay Gundogan, who has been diagnosed with the coronavirus, Pep Guardiola handed a debut to recent arrival Nathan Ake, and young phenom Phil Foden was also in the starting 11.
The pay-tv stations covering the game, Sky and DZAN, announced they would not be sending reporters to Budapest but instead would commentate on the game from Germany.
The top four finishers of each group will form a new group, to be based in Suzhou, to fight for the first to eighth positions of the season in the second phase, which will be held between October 16 to December 12.
Jiang Zhe (R) of Chongqing Dangdai Lifan vies the ball during the 12th round match between Chongqing Dangdai Lifan and Wuhan Zall at the postponed 2020 season Chinese Football Association Super League (CSL) Suzhou Division in Suzhou, east China's Jiangsu Province, Sept. 22, 2020. (Xinhua/Li Bo)
And all of this against a rival that in Gerard Moreno and Paco Alcacer has two of the best strikers in La Liga. Will it be a happy start for Koeman, or will he face problems from the very start?
About 10 minutes later, Chongqing enlarged the lead as Brazilian forward Fernandinho Silva cut in from the left, assisting his fellow peer Alan Kardec to make it 2-0 in the first half.