The victim was in a stationary traffic management vehicle when it was hit on the northbound side between junctions 14 at Stafford and 15 for Stoke-on-Trent at about 5am, police said.
Officers had been trying to stop the Audi, Staffordshire Police added.
A 27-year-old man has been arrested on suspicion of causing death by dangerous driving and remains in custody.
The M6 has been closed for several hours following the collision with delays of at least 60 minutes in the area, National Highways tweeted.
The man who died was in his 40s and was the only person in the traffic vehicle, detectives said.
They said they believed the Audi had previously been involved in an incident elsewhere in the West Midlands.
The crash has been referred to the Independent Office for Police Conduct due to the police activity before the collision.
