Dunn had already shot 8 episodes as the star of the show -- which featured the former "Jackass" star recreating famous stunts from TV shows, movies and video games.
According to Deadline.com, the show got off to a slow start ... with only 31,000 viewers tuning in to the Tuesday premiere.
A rep for G4 explained, "The show will not be airing for now and discussions are underway re future plans."
G4 released a statement saying, "All of us at G4 are shocked and deeply saddened by the tragic news that Ryan Dunn has passed away. Ryan’s comedic wit and signature no-holds-barred approach made him an incredible talent and his work on G4’s 'Proving Ground' was flawless."