David Pipe's charge fell at the final fence in the Byrne Group Plate when challenging in third place.
The 10-year-old receiving lengthy treatment on the course and the screens were still up during the next race, the Fulke Walwyn Kim Muir Challenge Cup Handicap Chase.
But vets were unable to save the animal and it was put down due to a major spinal injury.
The four-day Cheltenham Festival is the highlight of the National Hunt racing calendar but five racehorses died at the course in 2012.
The worst overall tally of fatalities during the Cheltenham Festival came in 2006 when nine horses died.
Amateur rider JT McNamara had a bad fall from Galaxy Rock in Fulke Walwyn Kim Muir Chase and left in an air ambulance. He will undergo further assessment at Frenchay Hospital in Bristol.
Dr Adrian McGoldrick was quoted as saying: "He has been put in an induced coma and airlifted to the regional spine unit where he will be scanned."
While jockey Davy Russell suffered a collapsed lung and will miss his ride on Gold Cup second favourite Sir Des Champs on Thursday.