"I wanted to swim into 15 minutes before the race, and the final went very smooth today," said Sun.
"The National Championships improved my confidence, and I will focus on the preparation of the Barcelona Worlds and try to improve my start," said Sun.
He also won the 200m and 400m titles in 1:44.99 and 3:42.93 respectively, which were also the world best results of the season. He claimed the 800m free in 7:48.60, which was the second fastest time of the year, as Olympic 1,500m runner-up Ryan Cochrane just timed a world best 7:43.61 on Wednesday's Canadian world-title trials.
The magic girl Ye Shiwen also collected four gold medals here. The London Olympic 200m and 400m medley champion showed her versatility as she won the 200m freestyle and backstroke in Zhengzhou.
Ye won the 400m medley in 4:34.27, which was about six seconds outside her Olympic winning result and the world record 4:28.43 on Monday.
"I was very tired," said the 17-year-old. "I took part in too many races which made me exhausted. I need time to take some rest."
Life aboard a fishing boat under bridge in city of Chongqing