The Paralympic athlete, who shot Steenkamp dead through a locked toilet door, told British broadcaster ITV she would want him to dedicate his life to charity, not waste it behind bars.
The 29-year-old gold medallist, known as the "Blade Runner" for his carbon-fibre prosthetics, is awaiting sentencing for her murder on July 6. Prosecutors have asked for at least the minimum 15-year jail term.
Steenkamp's family have not commented on his decision to give his first television interview since her death - though prosecutors have questioned why he felt unable to give testimony but was willing to talk to journalists, accusing him of showing no remorse.
"I don’t want to go back to jail. I don’t want to have to waste my life sitting there," Pistorius told ITV, which issued excerpts from the interview on Thursday.
He said that if he managed to avoid imprisonment, he would like to help the less fortunate.
"I would like to believe that if Reeva could look down upon me that she would want me to live that life," he said.
TEARS
The prosecution said Pistorius deliberately murdered his girlfriend after she locked herself in the bathroom during a late-night argument.
He argued that he had mistaken her for an intruder.
In the interview, filmed at his uncle's house in the capital Pretoria, Pistorius often broke down in tears as he described the events of that night.
"I opened the toilet door and immediately when I saw Reeva she was over the toilet," Pistorius said. "She had slumped over the toilet and at that point I knew that I had killed her."
ITV said that Steenkamp's family had declined an interview.
The athlete was originally jailed for five years for culpable homicide, South Africa's version of manslaughter, then released on parole after serving less than a year. But the conviction was later upgraded to murder on appeal.
Pistorius reached the pinnacle of his fame in London 2012 when he became the first double amputee to run in the Olympics, reaching the 400 metres semi-finals, before taking two golds in the Paralympics.
(Editing by James Macharia and Andrew Heavens)
