Most of the arrests were for drug possession or the sale of illegal products, a police spokesman told AFP, who said there were no major incidents at the three day festival in downtown Miami.
Last year, a 21-year-old man died of an overdose and a security guard was seriously injured when crowds pushed down a security fence trying to get in.
Ultra, which has been held since 1999 and had featured many of electronic music’s best known stars, draws about 100,000 people a day.
Some local authorities have asked that the festival be cancelled because of the incidents it generates and the congestion it causes in Miami.
This year’s event was headlined by David Guetta of France, the United States’ Skrillex, Carl Cox from Britain and Dutch performers Tiesto and Armin Van Buuren.