The race was immediately stopped as medics battled to treat Hegarty's injuries on the side of the track.
He died on his way to the hospital.
A statement from the race organisers on Twitter read: 'The Macau Grand Prix Committee extends its deepest sympathies to the family and friends of Daniel.'
They added in a separate statement: 'Daniel's family and team have been contacted, and the committee will ensure every assistance is extended to them.'
Hegarty, from Nottingham, who was a regular at the Isle of Man TT, had tweeted on Friday: 'Positive Q2 jumped from 19th to 15th with much more competitive times. Really thankful to the @TopgunRacing1 team for their hard work. Bike is much easier to ride now.'
He was taking part in his second Macau Grand Prix after finishing 16th last year.
Northern Ireland's Glenn Irwin was announced the winner after the race was stopped on the sixth lap.
Macau has been hosting the street race for cars and motorbikes since 1954.
Hegarty was the first rider to die at the event since Portugal's Luis Carreira was killed in qualifying for the 2012 race.
According to the BBC, organisers awarded the race to Irwin, although there were no anthems or champagne on the podium.
Speaking afterwards, the winner said it 'was not a celebration'.
He added: 'It's a very sad end to what has been a successful week. The win is all irrelevant now and I wouldn't have won the race had it gone the distance.
'It's a tragic end to the day. That's road racing and it's tough.'
Hegarty's girlfriend Lucy Draycott expressed her heartbreak on Facebook claiming she had lost 'the love of my life'.
Ms Draycott from East Bridgford said: 'It is with a broken heart to tell you that the love of my life passed away this morning.
'I just need time to take in what has happened and would appreciate if people could just be patient with me and wait for contact.'
Members of the Southern 100 International Road Races expressed their sadness at Hegarty's death.
Spokesman Phil Edge said: 'Dan from Bingham, Nottinghamshire made his Billown debut in 2016 taking three top-ten positions and his first podium, a third in the Island Aggregate Superbike race.
'Returning this year, riding the Top Gun machines, he once again took three top-ten placing's along with a sixth place in the prestigious Manx Gas Solo Championship race where he became a number of "elite" group of riders who lapped the 4.25-mile Billown Course at over 110 mph.
'It is a double tragedy for Top Gun Racing, as Gavin Lupton succumbed to injuries sustained at the Ulster Grand Prix earlier in the season.
'Southern 100 Racing extend its condolences to Dan's wife Lucy and his two boys, and to his family, racing team and friends at this extremely sad time.'