Federal Reserve Chair Janet Yellen has a fine line to walk in her debut press conference on Wednesday afternoon, but Jim Cramer thinks stocks will rally if she can tout the economic recovery and expresses concerns about growth, as well.
"This is one of those where if she comes on too strong about how strong the economy is, then people are going to say, you know what? Rates belong at 3 percent. Then you're going to have all the bond market equivalent stocks come down," Cramer said on "Squawk on the Street" on Wednesday. "So I think she needs to just be able to thread the needle, be saying, hey, you know what, it's pretty good, but it isn't good enough and that's how you go higher."
(Read more: Wall St eyes Yellen for possible job target shift)
Investors will likely parse her every word, but Cramer noted this isn't her first news conference—just her first time as Fed chair.
"I think that Yellen is a seasoned hand. I think that we all kind of think she's never had the mic. She's been behind the mic for years and years," Cramer said.
The FOMC's statement about its two-day meeting is due at 2 p.m. EDT, followed by Yellen's press conference 30 minutes later.
(Read more: Yellen's media debut: Plenty at stake politically)