The makers of Rust showed "plain indifference to recognised hazards associated with use of firearms on set", according to the New Mexico Environment Department.
The agency has issued the maximum $US136,793 fine to Rust Movie Productions.
Halyna Hutchins was killed and director Joel Souza injured in October as Baldwin rehearsed with what he believed to be a safe gun.
The actor, who was also a producer on the film, has previously said he did not pull the trigger and has no idea how a live bullet came to be on the set.
