Michael Lawrence, 57, was sentenced after being found guilty at Guildford Crown Court.
He was also given a lifetime restraining order and a sexual harm prevention order (SHPO), preventing him from ever contacting the victims again and from having contact with any other children.
The investigation began in 2016, when one of the victims came forward to report that they had been physically, sexually and emotionally abused by Lawrence between 2012 and 2015. A second victim was subsequently identified during the investigation.
Lawrence was arrested in October 2016 and charged with 21 offences. Following a two-week trial he was convicted of two counts of cruelty to a person under 16, five counts of causing a child under 13 to engage in sexual activity and three counts of assault of a child under 13 by penetration.
Detective Sergeant Jack Poynter, who led the investigation, said: “The court sentence handed to Lawrence reflects the predatory and vile nature of his behaviour towards the victims over the three years. He abused them in every way he could – sexually, physically and emotionally – and then threatened them if they dared to tell anyone about what he was putting them through.
“Thankfully, they were both able to find courage and speak out about their ordeal. Both victims are pleased with the result and they will now at last hopefully be able to begin their recovery, knowing that Lawrence has been locked away for a long time and that they are safe.
“I would like to pay tribute to them for their bravery in coming forward and giving evidence, without which we would not have secured the conviction against Lawrence.
“I would also like to thank the investigation team and highlight the efforts of all those involved in the enquiries.”
DS Poynter added: “We always treat reports of this nature extremely seriously, and will ensure they are fully investigated. If you have been the victim of a similar offence please come forward and talk to us, we will support you.”