Llewllyn Mitcham, 30, of Leeds, appeared before York Crown Court on Monday.
He pleaded guilty to causing serious injury by dangerous driving; driving while disqualified and driving with no insurance.
The court heard PC Thomas Lister, of North Yorkshire Police, was seriously injured when he was hit by a Vauxhall Insignia, which was driven by Mitcham on Bewerley Road in Harrogate on March 16.The case was adjourned for a pre-sentence report to be drawn up.
Addressing Mitcham, the Recorder of York, Judge Sean Morris said: "These are extremely serious matters. I can not see anything other than a custodial sentence following it. You better get your affairs in order.
"You have done the right thing in pleading guilty."
Mitcham will be sentenced at York Crown Court on May 17.
He was granted conditional bail.