After challenging for a top-four place throughout the previous Premier League campaign and winning the FA Cup the French defender knows they cannot afford to stay stationary next season.
Koscielny, who is preparing for the FIFA World Cup with France, believes Arsene Wenger has to improve the quality throughout the squad so that Arsenal can move forward, with a striker the top priority.
Olivier Giroud was Arsenal's leading goal scorer last season with 16 league goals but Koscielny says his France teammate needs more help and competition for his place.
"We'll need a goalkeeper, a right back, a midfielder and a striker," Koscielny said at France's pre-World Cup training camp.
"It's important to have a minimum of these four players so that we'll be better able to challenge over the course of a whole season against teams like Manchester City, Chelsea or (Manchester) United.
"We need to recruit a very, very good striker, because it's important for us, for competition for places, because Olivier needs that to become even better.
"Having a striker who scores more than 30 goals a season can help us win the Premier League.
"Compared to the squads like Manchester City, even United, Chelsea, you can see there's a certain difference."
Arsenal have been linked with moves for Loic Remy, Cesc Fabregas and Serge Aurier during the close-season but new signings are yet to arrive at the Emirates Stadium.
