The Isle of Wight youngster, who has twice beaten Phil Taylor in professional events, came through the last 64 of the £50,000 tournament in Reading on Saturday to set up a decider against Rowby-John Rodriguez.
Brown saw off Shaun Lovett 6-2 in the opening round before whitewashing Australian Robbie King to reach the last 16.
There, he defeated Holland’s Ryan De Vreede 6-2 and he followed it up with 6-3 victory against Adam Hunt, who was the number one seed.
Brown then booked his place in the final – at London’s O2 Arena – with a 6-2 triumph over Dutch ace Dirk van Duijvenbode.
“It’s a massive day for me, a life-changer,” admitted Brown. “I’ve been practising for four hours a day since Christmas Day, and this was the day I wanted the practice to pay off so thankfully it did.
“I’m so happy to be at The O2, and also in the Grand Slam of Darts, and hopefully I can win and get the place in the World Championship too.
“I’m only 21 so it would be nice to put my name on this trophy alongside the likes of Arron Monk, James Hubbard and Michael Smith, who’ve come through the Youth Tour system.”
Victory in the final, which is held as part of the Premier League finals night, would also see Brown qualify for the World Championships, while both finalists have sealed places at Grand Slam of Darts.
By Chris Murphy