Olympic and world champion Sun Yang dominated the men's 200m free final with a world top time so far this year at the National Swimming Championships on Saturday.

Sun, 23, who lost the gold of the event at the Asian Games last year to Japan's Kosuke Hagino, clocked one minute 45.75 seconds in the final, 0.07 second faster than Hagino's season best set at the Japan's national championships.

"I feel better than yesterday," said the star swimmer, who finished first in the 800m free preliminary earlier Saturday. "The result improves my confidence. I will also take part in the 800m and 1,500m. It's a tight schedule but I will take it as a practice of the world championships."

The National Championships is the first competition Sun take part in after the news broke by the end of last year that he served a three-month ban in 2014 after testing positive for the banned stimulant trimetazidine on May 17. He had a good start here by winning the 400m free on Thursday.

Sun's foreign coach Denis Cotterell was not allowed to coach him as a result of the new policy to be implemented by Swimming Australia.

The new policy forced Sun to train at other clubs in Australia, and according to Zhang Yadong, Sun's coach, Sun worked hard during the 13-week winter training, and lost some weight.

Another Australian coach, Brain King, now worked with Sun. King used to be Cotterell's assistant at the Miami Club where Sun used to train.

"Brain has different plans under different circumstances. I made improvement in my starts and turns," Sun said.

King also seemed happy with his job. "Our aim is the world championships," he said. "I hope we can do our training well and have a good relationship."

Saturday also produced several world top five results. Zhejiang's Fu Yuanhui won the women's 100m backstroke in 59.41, fourth fastest time in the world so far. Hubei's Chen Jie came second in 59.78, and Beijing's Cheng Haihua ranked third in 1:01.02.

The men's 100m back title was taken by Zhejiang's Xu Jiayu in 53.47, fifth in the world. Zhejiang's Li Guangyuan followed in 54.80, while Guangdong's He Jianbin third in 55.02.

Shandong's Xin Xin clocked the world fifth fastest women's 1,500m in 16:23.47, while Jiangsu's Shi Jinglin won the women's 100m breast in 1:07.03, also ranked fifth in the world so far the year.