The 23-year-old has been open about his desire to move in from the wide areas to pose more of an attacking threat on goal but Barnes believes that Walcott is better suited as a winger.
"I don't understand this whole idea of Theo Walcott playing up front," Barnes told talkSPORT. "Theo has been scoring goals from a wide position.
"Frank Lampard, and David Platt before him, got goals regularly but they didn't say, 'because we score, we want to play up front'. Theo has to understand that his best position is coming in from the wide areas, where he can still score his goals."
Walcott is expected to feature for England in tonight's friendly against Brazil at Wembley.