The four-time Olympic medallist won the 1,500-metre freestyle in a championship record time of 14 minutes, 44.10 seconds.
The mark fell more than 13 seconds short of his world record time but enough to easily win the race.
Of the nine gold medals available, eight went to Chinese swimmers.
Lu Ying, the Olympic silver medallist, won the women's 100m butterfly for her second gold. Japan's Kazuki Kohinata was the sole non-Chinese winner, when he came home first in the 200m breaststroke in a championship record time of 2:12.13 for his second gold.
Kohinata is only the fourth non-Chinese swimmer to win.
The Chinese set four championship records, including one by 13-year-old Xu Danlu, who won the 400m freestyle in a time of 4:05.75.
The heats provided another forgettable morning for the home contingent with no UAE representative - nor West Asian swimmer - qualifying for the evening finals.
Mohammed Al Ghafri came closest with an 11th fastest time in the 50m backstroke. His time of 28.10, however was two seconds off the pace set by Jiayu Xu of China. Al Ghafri's compatriot, Yaaqoub Al Saadi, was a further 2.89 secs slower to finish 17th of 21 competitors.
In the men's 100m freestyle, Kuwait's Mohammed Madouh missed out on qualification by just 0.17 secs, while the UAE's Obaid Al Jasmi and Al Ghafri finished 18th and 19th from a field of 30.
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