The Spaniard is expected to be appointed as successor to Arsene Wenger, who stepped down from the role following a 22-year spell at the end of the season.
Emery won five trophies, including the Ligue 1 title, during a two-year stint in charge of Paris Saint-Germain, but Ranieri believes that the 46-year-old will need time to find his rhythm.
"Unai is a good man and a good coach. He managed for a lot of years in Spain," Ranieri told Sky Sports News. "He made a very good season in Paris Saint-Germain, but you know in Paris you have to win the Champions League, and only the Champions League, that is the target there.
"I think now maybe [the new Arsenal manager] needs three [or] four years to stay calm and then restart, but football is fantastic because you never know what could happen.
"Unai is a very strong man, a good manager and I think he could have very good success there."
Emery also previously coached Sevilla, where he guided the club to three back-to-back Europa League crowns.