Robert Chisholm, 70, from Glasgow, was convicted of raping the first woman at his then home in Saltcoats, shortly after her 21st birthday party in 1978.
He later moved to Kilmarnock and raped the other woman, who was aged 20, after they had been out selling the church charity's War Cry magazine.
Chisholm was caught after one of the victims contacted police years later.
Jailing him at the High Court in Livingston, judge Lord Turnbull told Chisholm that he had abused the trust bestowed on him by his rank in the church charity.
He said Chisholm's name would remain on the sex offenders register for seven years.
A previous hearing at the High Court in Glasgow was told Chisholm served as a Salvation Army captain in Ayrshire in the late 1970s.
He was described as a "determined sexual predator". The court heard one of the victims became pregnant and had his child.
Chisholm was caught in 2014 when one of the women went to police sparking an investigation into his background.
Prosecutor Steven Borthwick said Chisholm had betrayed his position of trust in the most appalling way.
"Having carried out depraved sexual attacks, he instilled a fear that they would not be believed, ensuring their silence," he told the court.
After the verdict, it emerged that Chisholm left the Salvation Army in the early 80s.
Chisholm had denied all the allegations and did not give evidence during the trial.
John Keenan, defending, said there was little he could say in mitigation because Chisholm continued to deny responsibility for the offences.
He added: "He does at least recognize that he abused the position of trust he was in at that time in the Salvation Army."
A former Salvation Army captain has been jailed for seven years for raping two recruits more than 30 years ago.