QINGDAO, March 31 (Xinhua) -- Olympic champion Sun Yang fired off his personal-best 1,500m freestyle in four years and collected his fourth title on the last day of the Chinese Swimming National Championships here on Sunday.

Sun, who stormed three world-best time this season in 200m, 400m and 800m, led the field to win the the 1,500m freestyle in 14 minutes 55.00 seconds, his personal-best since 2015.

Ji Xinjie came to second in 15:03.38 and Cheng Long third in 15:10.80.

"It was the event I felt the most satisfied among all the four events I have competed. I beat the barrier of 15-minute and clocked my best time in four years since I changed my focus to the middle distance after 2012 Olympic Games," said the 27-year-old, the eldest one at the meet.

"I was so excited and happy because I found back my endurance for this marathon event and felt more confident in the mid-long distance events," Sun said.

Olympic champion Ye Shiwen continued her winning comeback in the 400m individual medley by claiming gold in 4:37.57. "Compared with 200m IM and 200m breaststroke, 400 IM was the weakest part of my events. But it was a good sign that I am a reborn swimmer," said the 23-year-old.

Asian record holder Liu Xiang crowned in her favorite 50m freestyle in 24.70, beating Wu Qingfeng's 24.77 and Zhu Menghui's 24.92.

"I did not feel good since this was the only event I competed in this meet. I expected a better time," said the 50m backstroke world record holder.

Xu Jiayu completed a golden-triple in the men's 50m backstroke with a time of 24.47 after he swept victories in 100m and 200m backstroke. Wang Peng took a silver in 25.17 and Li Guangyuan finished third in 25.28.

Team Zhejiang wrapped the men's and women's 4X100m medley relays in 4:02.50 and 3:37.51, respectively.

The eight-day competition, which attracted about 900 swimmers from 25 teams from March 24 to 31, serves as the qualifying tournament for the 2019 FINA Swimming World Championships in Gwangju, South Korea in July.