The 35-year-old crashed at Fisherman's Bend at the Guia circuit shortly before 4pm local time.
No other riders were involved in the accident.
A statement on the Macau Grand Prix's website read: "The medical services, a fast intervention vehicle, fully equipped, and an ambulance with two doctors in attendance - which were located at the side of the accident - immediately went to the rider's aid, and as a result of the doctors' diagnosis, Mr Carreira was immediately evacuated by ambulance to the hospital, where he was admitted at 16:08pm.
"Continuous CPR was performed, however he succumbed to his injuries at 16:28pm.
"The Macau Grand Prix Committee has contacted the family and the members of the team, and the committee expresses its sincere condolences."
The qualifying session was stopped after the crash and later abandoned.
Carreira raced for the Bennimoto Raider-Cetelem team.
The tragedy comes just over a year after Italian MotoGP rider Marco Simoncelli died after an accident during the Malaysian Grand Prix at Sepang on October 23, 2011.