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The former soldier, who rides with a prosthetic leg, won the Grand Military Gold Cup on Rathlin Rose (7-4 fav).
The horse, trained by David Pipe, won by 12 lengths.
Last month, 34-year-old Disney became the first amputee jockey to win at a professional racecourse in Britain when he guided the same horse to victory in the Royal Artillery Gold Cup.
"If anyone wants a one-legged jockey next week [Cheltenham Festival] I'll be kicking about"
"He is class, to win with an amateur like me on he has got to be pretty decent and I just try not to get too busy on him," said Disney.
Disney lost his lower right leg when his vehicle was hit by a grenade while serving in Afghanistan in 2009.
"Tonight I will have some pints with a mate and kick on point-to-pointing," he said.
"I love winning, like anyone else doing it. It's the most phenomenal sport. I loved my time in the army and the expeditions, but you don't replicate days like this very easily."
BBC Sport's Cornelius Lysaght
Terrific stuff from Guy Disney once again on Rathlin Rose, defying a bit of extra weight - and the pressure of a load of expectation - to record another emotional win.
Though this was mid-March, when reflections on 2017 are eventually gathered, Disney's two Sandown wins will surely become one of the great feelgood stories of the year.
From desperate injuries in Afghanistan, through rehabilitation and struggling to be granted a race-riding licence to the winners' circle at Sandown: what an inspiration to so many, in racing and well beyond.
He can ride a bit too…
Amputee jockey Guy Disney followed up his historic Sandown win with another victory at the course on Friday.