The Jamaican, who retained both titles as well as the 4x100m in London, said he has decided against switching to either the 400m or long jump.
"To do the three [sprints], that is the focus. I don't want to try any different events at Rio," he said.
"I will just defend my titles to show the world there's a possibility I can do it again."
The 26-year-old insisted he has no intention of easing off in his training.
He added: "It's all about hard work. When I was doing great when I was young, people used to say I was fast for my age, but I have put a lot of work into it since I was a senior athlete.
"I continue to work hard, continue staying focused and pushing myself.
"So for me that's the focus right now - to see how fast I can go and I definitely try to go faster each year."
Bolt became the first man to retain both Olympic sprint titles when he led home a Jamaica clean sweep in a time of 19.32 seconds in the 200m in London in August, with Yohan Blake in silver and Warren Weir in bronze.
It came after he had seen off Blake's challenge to win the 100m in 9.63 seconds, just 0.05 seconds slower than his own staggering world record, in what was a new Olympic best.
Speaking after he had completed his second Olympic sprint treble, Bolt had cast doubt on his participation in the events in Rio when he said: "My coach wants me to do 400m, I want to try long jump. It's just about making different goals, there's a lot of things I can do in the sport."