He is eligible for possible release after having served half his sentence.
But he first has to take part in a "restorative justice" process.
Pistorius shot Steenkamp dead in 2013 saying he mistook her for a burglar at his home in the capital, Pretoria.
The 34-year-old fired four times through a locked toilet door.
In 2014, he was given a five-year term for manslaughter.
But Pistorius was found guilty of murder on appeal in 2015 and the sentence was later increased to 13 years and five months.
