Barratt chief executive Mark Clare told the Sun: "We have one of the world's best armed forces. They have had a hell of a challenging period and all business should support those who have given so much."
The discount, which will launch on 27 June and run for the rest of the year, will be added to other incentives.
Clare said: "This should enable servicemen and women to own the roof over their heads. Prices have fallen by 25% in the past two years. We want to give them something on top."