Sun, who won three gold medals at the world championships in August, admitted he didn't have a driver's license and said the traffic police were still investigating him.
Calls to Hangzhou police were unanswered. Xinhua reported that after the accident police had not been able to find a record of his license and Sun had told them he did not have one. Xinhua said Sun faces a fine up to 2,000 yuan ($325) and a maximum 15-day detention.
A woman who answered the phone at the Chinese Swimming Association and refused to identify herself said the organization had heard about Sun's case and had no immediate comment.
A product of China's strict state sports system, Sun was formally censured by his training school in February after feuding with his coach and missing practice in order to make commercial appearances and spend time with his air hostess girlfriend.
He was docked a month's stipend, suspended from commercial endorsements and forced to make a public apology.