A pink banner from environment group Extinction Rebellion was seen being unfurled over sponsorship hoardings at Club Corner, as the Formula 1 cars left the grid for their formation lap.
Photographs later showed the protestors, dressed in black overalls and wearing T-shirts and masks with the group's logo, being led away from the side of the circuit.
A statement from the track said that the four individuals involved in the demonstration had been detained.
"During the race, Northamptonshire Police were made aware of four people who had been detained by Silverstone security inside the venue perimeter," said the statement.
"Officers are working closely with Silverstone Circuit and conducting a full investigation. Four people have been arrested and are in police custody."
Formula 1 has operated strict controls for the closed-door opening races of the season to ensure that only individuals who were complying with coronavirus protocols could enter the venue.
It is not the first time that protestors have used F1 races as an opportunity to publicise their cause. At the Belgian Grand Prix in 2013, Greenpeace staged a protest against Shell, which was the title sponsor of the event.