Series seven of the long-running sci-fi show is due to begin later this month, with six episodes airing this year and eight in 2013.
Smith revealed to The Sun that Moffat has already pitched ideas for the next series to him, and that fans are in for a treat.
The 29-year-old said: "His first episode sounds great.
"It hasn't been written yet but the idea is as brilliant and as mental as you'd expect from Steven. So there's a lot to look forward to.
"When Steven was going to pitch the next season to me not long ago, he said, 'Are you ready to cry?'"
Smith also discussed the ongoing plans for the show's 50th anniversary celebrations next year, and claims that fans won't be disappointed with what's in store.
He says: "We want to do 50 years - and everyone that's been associated with the show - justice. We want to go, 'Look, world, here is Doctor Who. It's 50 years old, a science fiction show, still going and going from strength to strength'.
"Steven will do something brilliant. He'll do something grand, or maybe something very simple, but he'll come to it as a fan.
"He'll go, 'What would I want to see?'"
Watch the trailer for series seven of Doctor Who below: