Brown, who was arrested in January, had said he would fight the charge that he hit his wife, Tomi Rae, during an argument at the home they shared in Beech Island.
Instead, the 71-year-old Brown forfeited his $1,087 bond and "basically, he says, 'I give up,'" assistant solicitor Anthony Odom said Monday.
Brown's bond covers the fine for the charge and there will be no jail time, Odom said.
Brown's attorney Jim Huff of North Augusta did not immediately return messages seeking comment.
Odom said the plea won't affect a pardon Brown received in May 2003 but he will have a conviction on his record.
South Carolina's Probation, Parole and Pardon Services board had unanimously granted Brown a pardon for seven convictions over a 10-year period, most involving weapons. The pardon came over opposition from the Aiken prosecutor's office, four police officers and the board's own investigator, records showed.