Dolphins general manager Chris Grier said Walton had been waived after the club were made aware of the allegations earlier Tuesday.
"We were made aware of a police matter earlier this morning regarding Mark Walton," Grier said. "We hold our players to a high standard and take these matters very seriously. We will have no further comment at this time."
The Miami Herald newspaper said Walton was detained after attacking his girlfriend in Davie, outside Fort Lauderdale, early on Tuesday.
Davie police said Walton had been charged with aggravated battery of a pregnant person.
The Herald quoted a police report as saying Walton shoved his partner "against a wall and punched her several times in the head and face."
Walton has faced repeated legal issues since being picked by the Cincinnati Bengals in the 2018 NFL Draft.
He was waived by the Bengals in April after being arrested three times during the off-season for offences ranging from misdemeanour marijuana possession, misdemeanour battery and unlawful possession of a firearm.
He was handed a four-game suspension on November 4 for violating the NFL's personal conduct and substance abuse policies in relation to his multiple arrests.