Rashford and Kane played the entirety of England’s unconvincing 1-0 World Cup qualifying win over Slovenia last night.
Manchester United teenager Rashford played on the left flank, with Kane as the lone striker.
But Merson says to beat the best teams in the world, the pair need to play together up top.
“I think he’s got to find a way of playing two up front,” Merson said on Sky Sports.
“He’s got to play three at the back and two up front. Teams won’t be able to cope with us with two up front.
“If you put Marcus Rashford and Kane up front, with Kane’s guile and everything and Rashford’s pace, we’ll petrify teams. We’ll petrify teams.
“We can’t keep the ball, we’re never ever going to pass a team off the pitch.
“We’re not going to keep the ball for 20-30 passes, you watch it and it’s like a hot potato.
“Let’s go and get the ball forward and play at 100mph like we do in the Premier League and teams won’t be able to cope with us.
“I watched Italy absolutely rip Spain apart in the Euros. One reason: they played two up front.
“The defenders didn’t know what to do, they play against one every week.
“You’ve got to play two up front and have a go.”
Harry Kane has been nominated for Premier League player of the month for September after a blistering few weeks.
As for Rashford, he boasts six goals for club and country this term.