Show secretary Mark Stoddart said damage caused by the weather overnight was “substantial”.
“We had a lot of the trade stands down, it just was not safe,” he said.
“It’s starting to get more substantial than that, bins are starting to blow in the wind, tables, chairs are blowing over, and it’s just not a safe environment for people.
“There is a long, long list of people that come together to put this on and in some respects, I’m sorry we are having to cancel, but that unfortunately is the best option we have.”
Organisers said more information for ticket holders and stakeholders would be communicated through the Royal Cornwall Show’s official channels as soon as possible.