McLaren has confirmed it will run the the 18-year-old in the session which will be the Brit's first outing during a grand prix weekend.
Norris, who is the reserve driver at the Woking team, has recently driven for the operation in a test following he Hungarian Grand Prix.
McLaren announced last week that Carlos Sainz will take over the seat vacated by Alonso following the double world champion's exit from the sport at the end of the year.
Norris was approached by Toro Rosso to take over Brendon Hartley's drive earlier this year.
“This weekend will be the first time that our reserve driver Lando will drive the MCL33 during a race weekend, as he steps into Fernando's car for FP1 on Friday.
“This is not only part of his ongoing development, but also the evaluation and performance evolution of the car,” said sporting director Gil de Ferran.
“We'll be taking a strategic view race-by-race at where else this might be beneficial for us over the coming grands prix.
“Spa-Francorchamps has a well-deserved reputation as a racers' circuit due to its historic significance and popularity among the drivers.”
Opening practice for the Belgian Grand Prix will begin at 1900 AEST.