BAOJI, China, April 9 -- China's Olympic and world champion Sun Yang won the men's 400-meter freestyle at the National Championships here on Thursday.

Sun clocked three minutes and 44.53 seconds, which ranked third in the world this season. Australia's 18-year-old Mack Horton claimed the world best time 3:42.84 recently, who will be one of Sun's big rivals at the world championships this July in Kazan.

"It is a good start," Sun said. "The most important thing for me is the world championships this year. I am not in my best, but I still have time."

It was Sun's first competition after the Asian Games last year. Henan's Li Yunqi took silver in 3:50.73, while Tianjin's Tong Yang came third on 3:50.74.

In the women's 400m free, Shanxi's Cao Yue touched first in 4:05.86, which ranked ninth so far this year. Zhejiang's Shao Yiwen ranked second in 4:07.01 while Liaoning's Guo Junjun was third in 4:07.34.

Guangdong won the men's 4x100m freestyle relay in 3:19.27, and Zhejiang was the winner of the women's 4x100m free relay with a 3:39.75 result.