The RDS will spend £1 million on the equestrian facilities at the Ballsbridge showgrounds over the next three years.
The announcement was made by Mr Shane Cleary, the RDS chief executive, as the Kerrygold Horse Show ended this weekend.
Mr Cleary also announced that the society plans to go ahead with plans to build a £3 million to £5 million conference centre with or without the support of the Government.
He said the Government intended to re-invite tenders for the new national conference centre and the RDS had not yet decided whether it will take part.
"We will go ahead with our own plans if proposals for the national conference centre go much beyond next spring," he said.
The equestrian development, he said, will take place over three years and include the building of a new stabling/exhibition hall to the east of the main hall.
There will be an extension of the stabling areas in the Paddocks North and South areas, a new fodder store, an all-weather sand paddock and a new ring in Simmonscourt.
He said Pembroke Hall will be renovated as a bar and catering facility and the Anglesea stand will be refurbished to include modern plastic seating, a new judges' box, president's box and better media facilities.
Mr Cleary said that there had been a lot of confusion created by the cancellation of the World Equestrian Games both here and abroad.
"What we are saying here is that these renowned grounds with their world-wide reputation will stage the 125th Horse Show next year, and this investment will ensure the continuation of the show.
"I want to make the clearest possible announcement. The RDS is not finished."