The 46-year-old actor said Saldana would be his first choice as he thinks the actress would be great as She-Hulk, reported Deadline.
"Well I think Zoe Saldana would be a great She-Hulk. It'd be nice to see someone like her join the Avengers. Or someone quiet and demure like Emma Stone would be nice. But it would be up to the powers that be," he said.
Both actresses have prior experience in Marvel Comics movie adaptations.
Stone starred as Gwen Stacy in Marc Webb's two 'Amazing Spider-Man' films at 20th Century Fox.
Ruffalo recently revealed that Marvel is considering a new Hulk solo movie.
Joss Whedon's sequel 'Avengers: Age of Ultron' will be released in the UK on April 24, 2015 and in the US on May 1.
