Xu Jiayu celebrates after winning the men's 100m backstroke final during the swimming competition at the 2017 FINA World Championships in Budapest, July 25, 2017. [Photo/VCG]

Xu, who ranked first in Monday's heats and semifinals, built his leading position from the start and finished atop the podium with 52.44 seconds, beating his American opponent Matt Grevers, the London Olympic champion, by four hundredths second.

"I didn't expect to win by such a small margin. The result was not quite up to my expectation, but in the end I won the title," said Xu. 

"I felt a little tired in the final part of the race, and did not feel as smooth as in the semifinals, because it had much impact on the podium position," he added. 

Xu finished 51.86 seconds in National Championships in April, just one hundredth second shy of the world record set by Ryan Murphy of the United States last year in Rio. Olympic champion Murphy got the bronze medal at 52.59 seconds. 

"I performed quite well in the semifinals, so it was normal for me to have some ideas in my mind. Actually I aimed at rewriting the world record before the matchup. 

"This time it could be seen as a surprise, and I lived up to my expectation, while failing to give myself some surprises," Xu pointed out. 

Before Xu's triumph, Chinese swimming star Sun Yang clinched his first gold medal in men's 200m freestyle at the World Championships. 

"I could also stand at the stage center now, just like he did," Xu said confidently.