Minister for Primary Industries Ian Macdonald says the change affects most of the Illawarra, Southern Highlands, Blue Mountains, Hawkesbury, Putty and central tablelands districts - previously in the amber zone.
He called it another major step towards progressing NSW to total freedom from EI in March.
"It means more than 95 per cent of NSW is now in the white zone.
"The only requirement for moving horses within the white zone is that a Travelling Horse Statement (THS) must be completed before the journey and carried during the journey.
"Providing no new infections are discovered, I'm confident that all of NSW will very soon be confirmed EI free, allowing horses to move anywhere in NSW if they have a THS."
NSW chief veterinary officer Bruce Christie said even though the last known infection had been cleared, it still remains crucial for horse owners to adhere to movement restrictions and report sick horses.
"We believe we have EI under control and we are now working to prove it has been wiped out by testing thousands of horses to confirm there are no remaining pockets of infection," Mr Christie said.
"Restrictions need to remain in place until we complete the proof-of-freedom testing.
"It remains vital to keep checking horses for EI and reporting sick horses, so that we can act swiftly and decisively if a new infection is located.
"In the unlikely event that a new infection is detected, we have contingencies in place that can be implemented locally without affecting the status of the rest of the state."
All remaining amber areas in the Wingecarribee, Wollondilly, Blue Mountains, Lithgow and Hawkesbury local government areas have now joined the white zone, along with parts of the Wollongong, Mid-western Regional, Cessnock, Singleton and Muswellbrook amber zones.
Full details on the zone changes are available at www.dpi.nsw.gov.au/equine-influenza.