Wenger has used the system recently and the Gunners beat Manchester City 2-1 in the semi-final of the FA Cup on Sunday.
He keeps faith with the formation but makes a few changes with Walcott coming in to replace Olivier Giroud as the leader of the attack.
Elsewhere Alex Oxlade-Chamberlain is rested after picking up a knock against City, with Hector Bellerin replacing him, whilst Francis Coquelin and Kieran Gibbs come in for Granit Xhaka and Rob Holding.
Leicester stick with their 4-4-2 formation with Jamie Vardy and Leonardo Ulloa up front.
Wilfred Ndidi and Danny Drinkwater play in the centre of midfield with Riyad Mahrez and Marc Albrighton on the wings.
Read the full article on eurosport.co.uk: Walcott leads line, Arsenal stick with three at the back