With the crowd enjoying warm early evening sunshine the day has already seen performances from all girl pop group The Saturdays, Daniel Merriweather, Friendly Fires and this year's Critics Choice Brit award winner Florence & The Machine.
Leaving the stage following his main stage set, Calvin Harris, who recently went to number one with I'm Not Alone, said: "It went off in the end, so happy days. It's good, I love Swindon, and I'll come back to Swindon maybe on a holiday!"
Dizzee at Radio 1's Big Weekend
Bethan, 16, from Lyneham in Swindon told Newsbeat she was glad that Big Weekend had come to her local area.
She said: "It's so great that it's come to Swindon. I'm really looking forward to seeing The Script, they're my favourite band."
Other artists playing across the event's four stages on Saturday include Basement Jaxx, Dizzee Rascal, The Wombats, Kasabian and DJ Chris Moyles.
The free festival, organised in a different UK location each year, has previously visited Preston and Dundee.
Madonna and The Kooks headlined last year's bash in Maidstone, Kent.
Day two [10 May] will see The Prodigy, Lily Allen, Ne-Yo, Franz Ferdinand, The Enemy and White Lies wrap up the weekend.
The weather is expected to be cloudy with sunny intervals on both days.