Andrew Hocking, 57, of West Sussex, sexually assaulted four girls, aged between six and 12, from 1976 to 1990 in Gloucestershire and Hampshire.
He was found guilty of one count of rape and six indecent assaults following a trial at Lewes Crown Court.
Sussex Police said Hocking showed "no genuine remorse" for his actions.
"Hocking stands out as cold, calculating, predatory and ruthless," said Det Con Chris Smith.
"Despite the strong evidence against him, he put the victims through the ordeal of having to recount their episodes of abuse."
Detectives discovered records of allegations of indecent assaults on a seven-year-old girl at his home in Alveston, Gloucestershire in 1976 and 1977, while they were investigated him over the making of indecent images of children.
Police were contacted by three woman claiming they had been attacked, when they were aged six, seven and 12, by Hocking at his address in Fareham, Hampshire, in the 1980s and 1990, following an appeal for information.
Following a trial, Hocking was convicted of one count of rape and six indecent assaults and cleared of one indecent assault.
The 57-year-old admitted making indecent images of children and possession of extreme pornography at an earlier hearing.
He was ordered to be put on the sex offenders register for life.

An Environment Agency severe flood warning - meaning danger to life - was removed from the A361 between East Lyng and Burrowbridge on 10 March.
Residents in the area saw their homes cut off and experienced long diversions as a result of the closure.
The road has been inspected by council highways officers and reopened at 17:00 GMT.
There is still some water on a short stretch of the road and Somerset County Council said temporary traffic lights will be installed to protect the carriageway and allow motorists to pass safely.
Councillor Harvey Siggs, responsible for Highways, said: "I'm delighted the A361 is to reopen at long last.
"Our highways teams have been working hard all week to clear the road and make sure it is safe, and I would like to publicly thank them for their efforts to get this key route open before the weekend."
A further inspection will take place early next week and the temporary traffic lights will be removed as soon as the remaining water has receded and the road judged to be safe, the council said.
Mr Siggs added: "Although the road is clear, the rhynes at the side of the road remain full of water so I would urge motorists to take extra care when driving, particularly in the foggy conditions we have seen over the last few days."
The clear-up of the A361 started on Monday with the removal of fallen trees and the cutting back of damaged vegetation.
Around 30 tonnes of used sandbags were removed before a sweeping and cleaning operation covered the 1.5 mile section of carriageway.
The council said that the road closure on the A372 Langport Road will remain in place next week for the removal of flood pumps.
With improving weather conditions the large temporary pumps at Beer Wall, near Aller, are no longer needed, it added.
The Environment Agency expects to begin removing the pumps on Monday and work is likely to take up to four days.
The road will remain closed after the pumps have been removed so the council can assess flood damage and carry out emergency repair works.

The album, currently untitled, will be released in the autumn by Motown Records.
"If your a rapper I suggest you run because I'm about to come for all of you sucka's," Hart wrote in a strongly worded post on Instagram.
"Y'all just knocked on the door of a small giant that loves chicken nuggets and long walks in the park."
Hart achieved fame as a stand-up before enjoying further success as the star of such films as Get Hard, The Wedding Ringer and Ride Along.
He has already been seen this summer in the action comedy Central Intelligence, alongside Dwayne "The Rock" Johnson.
And he can be heard in hit animated film The Secret Life of Pets as the voice of a short-tempered rabbit named Snowball.
The 37-year-old's previous albums have all been recordings of his stand-up shows.
A paedophile, branded "calculating and predatory", has been jailed for 15 years for a string of sex attacks on girls as young as six years old.
[NEXT_CONCEPT]
A road on the Somerset Levels which closed in December when it was engulfed by flood water has finally reopened.
[NEXT_CONCEPT]
US comedian Kevin Hart has signed a deal to release an album as his inept rapper alter-ego Chocolate Droppa.