The fire brigade were called out to the fire at Studland Heath, a Site of Special Scientific Interest, earlier on Tuesday evening and they warned members of the public to stay away from the park.
Two fire crews from Swanage were at the scene, as well as a unimog from Wareham and other equipment from across the county.
A spokesperson for the brigade told the Mirror Online: “We received a call at 8.26pm this evening from a member of the public who could see a lot of smoke coming from Studland Heath.
“Crews from Swanage (two), Westbourne, Poole, Christchurch, Hamworthy and Wimborne along with Land Rover pumps from Swanage, Poole, Hamworthy and Bere Regis, the Unimog from Wareham and a water carrier also from Poole are currently in attendance.
“Approximately 600 square metres of heathland is well alight, and our crews are working hard to put in a fire break to protect neighbouring properties.”
They tweeted earlier: “We’re currently dealing with a heath fire on #StudlandHeath
“#Dorset Strong winds are driving the fire and smoke, please avoid the area where possible.”
People were able to see the fire from Poole, which is around five miles away.
One person wrote on Twitter: “Looks like there’s a big fire over in the Purbecks at Studland. You can see it from the cliffs at Southbourne.”
Another tweeted: “It looks like a massive fire.”
In 2010, four acres of forest at Studland Heath were destroyed by a similarly large fire.