A stilt walker, gunslinger and puppeteer will be on site to boost support for the market, which has seen a recent decline in footfall.
The building is earmarked for demolition to make way for a multi-million pound cinema complex, with traders moving into a new market hall under the historic canopy.
Joe Gosney, who runs incense and fragrance stall Kaelia in the indoor market, is one of the traders behind the event.
He said: “It is mainly to re-enforce that the market is still open, we are still here for trade, and to remind people we’ve got a great market here in Preston.
“I think most traders would agree footfall has dropped off now because of people thinking the market has gone, so we are trying to remind people we are still here and to continue trading with us, because if we have a good market now, it puts everything in place for the future.
“We’ve got great potential here.”
Joe, who is looking to move his business into the new market hall when it is built, said the event would include a DJ on the balcony outside, a stilt walker, puppeteer, gunslinger and a Mad Hatter’s tea party being hosted.
He said there would also be craft stalls from across Lancashire and a “great atmosphere”.
He said: “It’s just to remind people of what great things we’ve got going on.
“Sometimes you don’t need an excuse for a celebration.”
He said some traders had been concerned about the market plans initially but said: “I think, now people have seen it, it’s turning very positive and I think a lot of the traders are behind it. I’m definitely one of those.”