More than 140,000 people are expected over four days
Royal Show organisers are confident this year's event will pass without a hitch after last year's show was forced to close a day early.
Muddy conditions forced the Warwickshire show, one of the largest agricultural shows in Europe, to close.
Organisers say this year the site is dry. But some animal numbers are down markedly due to movement restrictions to counter bluetongue disease.
The four-day event takes place at Stoneleigh Park.
A spokesman said last year's show had been affected by extremely wet weather throughout June while this year the site was dry.
However, restrictions on animal movements in bluetongue surveillance and protection zones has reduced the number of animals on show, with cattle down by 1,000 to only 200.
The number of sheep is down from about 1,600 to 400.
National Farmers' Union spokesman Alistair Johnson said it was "disappointing" for the public and the show but the precautions were vital for protecting livestock.
Highlights will include a visit from the Prince of Wales and the Duchess of Cornwall on Friday.
Meanwhile, more than 5,000 school children are expected to visit during the first two days.
Farmers have been affected by the restrictions
Royal Show spokesman Denis Chamberlain said that last year's heavy rain throughout June had meant the ground was saturated before the show got under way.
"Then, when we got more rain it could not run off," he said.
"This year, the showground is in a perfect condition. Conditions on Thursday morning were perfect, it was cool and a little damp."
This year, for the first time, the Royal Show is being held over a weekend so more people can visit.
Organisers said they normally expected up to 140,000 visitors, but were hoping for increased figures this year.