The Ivorian attacker has impressed during his first months with the Gunners.
"I watch a lot of the French league at home so I knew when Gervinho arrived that he was a very good player," Song told Arsenal's Official Matchday Programme.
"I'm not surprised to see him doing well here and I think there's more to come. It's not easy to come to the English league, it's harder and stronger, but he's getting used to it and I'm really happy to see him making a difference in games.
"Gervinho is a very quiet guy, not one who talks too much, but I think it's normal that you look and listen when you arrive somewhere before saying a lot.
"I think he's now coming out of himself and you can see it on the pitch too."