A fundamentalist church pastor had sex with two of his teenage daughters to educate them on how to be good wives, a South Australian court has heard.

The 54-year-old man, who cannot be named, was today sentenced in the SA District Court to eight and a half years jail after pleading guilty to seven counts each of incest and unlawful sexual intercourse.

The court heard that the man had sex with his daughters for nearly a decade from 1991 when they were aged 13 and 15 at the family property.

The sex took place at various locations including in a shearer's shed, a paddock, on the back of a ute and, on one occasion, at the girls' grandparents house.

The man told the court the sex was not about fulfilling his desires but about teaching his daughters how to behave for their husbands when they eventually married, as dictated in scripture.

In sentencing, Judge David Lovell said the misrepresentation of scripture used to justify the abuse of the girls "defied belief", and that he had "hypocritically betrayed" his religion and principles.

"You said the acts were about learning about sex rather than engaging in the acts of sex," Judge Lovell said.

"I do not accept that.

"You treated your daughters as your property ... using them to satisfy and gratify your sexual urges."

Judge Lovell gave full credit for the man's guilty pleas, saying he was genuinely remorseful and had a good chance of rehabilitation as his wife and the church remained supportive.

The man will be eligible for parole in four years.

AAP