Nigel McDermott, 53, contacted who he thought was a teenage girl online and arranged a rendezvous in Crawley.
The builder’s merchant was in fact contacting an undercover police officer, instead of a 13-year-old.
Sussex Police said no child was ever at risk during the investigation, and arrested him at a car park in Tilgate Park.
But McDermott appeared at Hove Crown Court where he admitted facilitating a child sexual offence. He was jailed for three years.
Investigator David Sharpe said; “McDermott engaged in online contact with someone he thought was a 13-year-old girl, but who was in fact a police officer.
“This arrest followed a proactive, intelligence led investigation, part of our continuing priority to protect children from sexual exploitation and from those who seek to do them harm.”
McDermott, of Hawks Ridge, Harnham, Wiltshire, will be a registered sex offender and was put under the terms of a Sexual Harm Prevention Order which cuts his access to children and computers.
The investigation was led by the Police Paedophile Online Investigation Team and the South East Regional Organised Crime Unit.
Victims of child sex abuse can contact 101 and speak with investigators.