The Westpac Rescue Helicopter flew to the scene about 4pm and were preparing to winch the man from the remote location.

He is believed to have suffered chest and head injuries.

RFS spokesman Ben Shepherd said paramedics who were nearby at the time treated the man.

He was being flown to John Hunter Hospital.

The fire in the Wollemi National Park and Putty State Forest is still being controlled but there is no immediate threat to properties.

The injured firefighter was not in an active fire ground at the time of the accident.