The Twilight star said that she is nervous because On The Road is an adaptation of the classic Jack Kerouac novel of the same name.
"I play Marylou and I am f**king freaking out about it," Stewart told The Daily Telegraph.
"Nobody has ever tried to make it and yet; it is insanely iconic. It is my favourite book and it's so f**king cool that I am doing it."
Stewart stars alongside Garrett Hedlund, Sam Riley, Kristen Dunst and Viggo Mortensen in the adaptation.
Boyfriend Robert Pattinson is reported to be keeping a close eye on her as filming continues in Quebec.