Walcott apologised in the aftermath of their 1-1 draw last week for attempting to win a penalty by diving.
Grayson said: "I have not spoken to the lad but he apologised on television.
"To be fair, he was honest enough to admit what he did. But it is an area I don’t agree with. If players get caught diving, they should be banned for the next game.
"Then, suddenly, people trying to influence decisions will stop. I feel there needs to be a ruling to cover if the referee misses it and then sees it afterwards.
"To be fair to Walcott, you don’t see many being as honest as that. He will have learned his lesson but if he’s playing, our fans will make their feelings known."