A 73-year-old Perth man is likely to spend the rest of his life in jail after being sentenced to 16 years for sexually abusing six children, including four of his own.

The man was convicted in the District Court on 24 counts of child sex abuse which took place over a 15-year period.

One of the victims, Cheryle Warner, was a ward of the state when the abuse began in the mid-1960s.

She says she was not believed when she first reported the crimes but she is encouraging other victims of child abuse to come forward ahead of the Royal Commission into child sex abuse.

"Never stop, never ever stop shouting your truth," she said.

"Just keep shouting until someone listens and takes hold of it and goes with it for you. Don't ever give up."

The man will be eligible for parole 12 years from now.